Methods and structures to prevent sidewall defects during selective epitaxy

ABSTRACT

Trenches (and processes for forming the trenches) are provided that reduce or prevent crystaline defects in selective epitaxial growth of type III-V or Germanium (Ge) material (e.g., a “buffer” material) from a top surface of a substrate material. The defects may result from collision of selective epitaxial sidewall growth with oxide trench sidewalls. Such trenches include (1) a trench having sloped sidewalls at an angle of between 40 degrees and 70 degrees (e.g., such as 55 degrees) with respect to a substrate surface; and/or (2) a combined trench having an upper trench over and surrounding the opening of a lower trench (e.g., the lower trench may have the sloped sidewalls, short vertical walls, or tall vertical walls). These trenches reduce or prevent defects in the epitaxial sidewall growth where the growth touches or grows against vertical sidewalls of a trench it is grown in.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a U.S. National Phase Application under 35U.S.C. §371 of International Application No. PCT/US2013/058084, filedSep. 4, 2013, entitled METHODS AND STRUCTURES TO PREVENT SIDEWALLDEFECTS DURING SELECTIVE EPITAXY.

BACKGROUND

Field

Circuit devices and the manufacture and structure of fin based circuitdevices.

Description of Related Art

Increased performance in and yield of circuit devices on a substrate(e.g., integrated circuit (IC) transistors, resistors, capacitors, etc.on a semiconductor (e.g., silicon) substrate) is typically a majorfactor considered during design, manufacture, and operation of thosedevices. For example, during design and manufacture or forming of metaloxide semiconductor (MOS) transistor devices, such as those used in acomplementary metal oxide semiconductor (CMOS), it is often desired toincrease movement of electrons in N-type MOS device (n-MOS) channels andto increase movement of positive charged holes in P-type MOS device(p-MOS) channels. However, performance and movement are slowed bylattice mismatches and defects generated in a between layers ofmaterials used to form the MOS.

For some CMOS implementation, the co-integration of lattice mismatchedmaterials like III-V material epitaxial growth on Silicon is a bigchallenge. Currently there is no state of art solution to co-integraten- and p-MOS material epitaxial growths on to a single Siliconsubstrate. Thus, in current applications, due to large lattice mismatchin materials, defects are generated when novel materials (III-V,Germanium (Ge)) are grown on a Silicon material substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross section view of a portion of a semiconductorsubstrate base after selectively, epitaxially growing a type III-V or aGermanium (Ge) material on a top surface of a substrate material in atrench between shallow trench isolation (STI) regions.

FIG. 2 is a schematic cross section view of a portion of a semiconductorsubstrate base after selectively, epitaxially growing a type III-V or aGermanium (Ge) material on a top surface of a substrate material in atrench having sloped sidewalls.

FIG. 3 is a schematic cross section view of a portion of a semiconductorsubstrate base after selectively, epitaxially growing a type III-V or aGermanium (Ge) material on a top surface of a substrate material in acombined trench having an upper trench over and surrounding the openingof a sloped walled lower trench.

FIG. 4 is a schematic cross section view of a portion of a semiconductorsubstrate base after selectively, epitaxially growing a type III-V or aGermanium (Ge) material on a top surface of a substrate material in acombined trench having an upper trench over and surrounding the openingof a tall vertical walled lower trench.

FIG. 5 is a schematic cross section view of a portion of a semiconductorsubstrate base after selectively, epitaxially growing a type III-V or aGermanium (Ge) material on a top surface of a substrate material in acombined trench having an upper trench over and surrounding the openingof a short vertical walled lower trench.

FIG. 6 is a schematic top view of a portion of a semiconductor substratebase having combined trenches formed over the base.

FIG. 7A shows a semiconductor substrate after covering areas of the topsurface of the substrate where trenches are to be formed with a mask;and exposing unmasked areas of the top surface of the substrate next tothe masked areas to a wet chemical etchant that etches the substrateanisotropically to form trenches which have outward sloping between 40degrees and 70 degrees (e.g., such as 55 degrees) sidewalls.

FIG. 7B shows the semiconductor substrate of FIG. 7A after filling thebetween 40 degrees and 70 degrees (e.g., such as 55 degrees) outwardsloping trenches with shallow trench isolation (STI) material.

FIG. 7C shows the semiconductor substrate of FIG. 7A after removing themasks of the original areas of the top surface of the substrate thatwere covered with the masks to expose the top surface of the substratethere.

FIG. 7D shows the semiconductor substrate of FIG. 7A after etching theexposed original areas of the top surface of the substrate usingisotropic etching; thus providing trenches in oxide with between 40degrees and 70 degrees (e.g., such as 55 degrees) inward-slopingsidewalls, with the silicon exposed only at the bottom of the trench.

FIG. 7E shows the semiconductor substrate of FIG. 7A after filling inthe lower trench having between 40 degrees and 70 degrees (e.g., such as55 degrees) inward-sloping sidewalls with another mask.

FIG. 7F shows the semiconductor substrate of FIG. 7A after patterningand etching the new, other mask to form openings to the old STI regions,thus creating larger square mesas of the new mask over the lower trench.

FIG. 7G shows the semiconductor substrate of FIG. 7A after filling theopenings to the old STI regions with shallow isolation-oxide (STI)material.

FIG. 7H shows the semiconductor substrate of FIG. 7A after polishing thenew STI isolation-oxide to expose the larger square mesas of the new,other mask and the new oxide/STI in the openings to the old STI regions.

FIG. 7I shows the semiconductor substrate of FIG. 7A after selectivelyetching or removing the larger square mesas of the new, other mask overthe lower trench without removing any new oxide, so that the new oxidein the openings to the old STI regions remains; thus providing an uppertrench in oxide with vertical sidewalls and having a lower opening overand surrounding an upper opening of a lower trench having between 40degrees and 70 degrees (e.g., such as 55 degrees) inward-slopingsidewalls.

FIG. 8A shows a semiconductor substrate after covering areas of the topsurface of the substrate where trenches are to be formed with a mask;and exposing unmasked areas of the top surface of the substrate next tothe masked areas to a dry chemical etchant that etches the substrateanisotropically to form trenches which have vertical sidewalls.

FIG. 8B shows the semiconductor substrate of FIG. 8A after filling thevertical sidewall trenches with shallow trench isolation (STI) material.

FIG. 8C shows the new STI material planarized to a height to exposesurfaces of substrate; to expose top surfaces of STI material regions inthe trenches; and to remove the masks.

FIG. 8D shows the semiconductor substrate of FIG. 8A after etching theexposed original areas of the top surface of the substrate usingisotropic etching; thus providing trenches in oxide with verticalsidewalls, with the silicon exposed only at the bottom of the trench.

FIG. 8E shows the semiconductor substrate of FIG. 8A after filling inthe lower trench having vertical sidewalls with another mask.

FIG. 8F shows the semiconductor substrate of FIG. 8A after patterningand etching the new, other mask to form openings to the old STI regions,thus creating larger square mesas of the new mask over the lower trench.

FIG. 8G shows the semiconductor substrate of FIG. 8A after filling theopenings to the old STI regions with shallow isolation-oxide (STI)material.

FIG. 8H shows the semiconductor substrate of FIG. 8A after polishing thenew STI isolation-oxide to expose the larger square mesas of the new,other mask and the new oxide/STI in the openings to the old STI regions.

FIG. 8I shows the semiconductor substrate of FIG. 8A after selectivelyetching or removing the larger square mesas of the new, other mask overthe lower trench (e.g., nitride) without removing any new oxide, so thatthe new oxide in the openings to the old STI regions remains; thusproviding an upper trench in oxide with vertical sidewalls and having alower opening over and surrounding an upper opening of the lower trench.

FIG. 9 is an example process for forming a single trench with (or acombined trench having a lower trench with) between 40 degrees and 70degrees (e.g., such as 55 degrees) inward-sloping sidewalls between STIregions, with a substrate top surface exposed at the bottom of thetrench.

FIG. 10 is an example process for forming a trench vertical sidewallsbetween STI regions, with a substrate top surface exposed at the bottomof the trench.

FIG. 11 illustrates a computing device in accordance with oneimplementation.

DETAILED DESCRIPTION

Large lattice mismatch in materials may generate defects (e.g., defectsin the crystal lattice of the material) when certain materials (e.g.,type III-V, or Germanium (Ge) materials) are epitaxially grown on aSilicon material substrate (e.g., single crystal silicon). In somecases, the materials may be epitaxially grown from a substrate surface,and “selectively” grown on the surface in trenches between shallowtrench isolation (STI) regions. Defect density improvements may beaccomplished by growth optimizations/tricks in blanket film growths.However, there may not be a reduction of such defects for selectiveepitaxial material grown in a trench. If these defects propagatethroughout the trench, they can lead to slower or decreased performance,reduced yield, and variation issues in circuit devices built on a devicelayer formed from epitaxial growth extending above the trench. Thispropagation may exist in “fin” devices (e.g., circuit devices) formed infins that are patterned and etched from epitaxial growth (e.g., devicematerial, regions or layers) extending above the trench. In some cases,a pair of device fins are patterned and etched from the growth, such asthe growth extending above each trench. Such fin devices may include finintegrated circuit (IC) transistors, resistors, capacitors, etc. formedin or on sidewalls of “fins” grown from or extending above asemiconductor (e.g., silicon) substrate or other material. Such devicesmay include fin metal oxide semiconductor (MOS) transistor devices, suchas those used in a complementary metal oxide semiconductor (CMOS) basedon movement of electrons in N-type MOS device (n-MOS) channels andmovement of positive charged holes in P-type MOS device (p-MOS)channels.

In some cases, a “buffer” material may be selectively epitaxially grownfrom a substrate surface, in the trenches. The buffer material may begrown or used so that crystalline defects are trapped or removed below atop surface of the buffer material. Then, a “device” material may begrown from the top surface of the buffer material. This way, the devicematerial may have fewer or be free of such defects, thus providingfaster or increased performance, increased yield, and fewer variationissues in circuit devices built on or in the device material.

FIG. 1 is a schematic cross section view of a portion of a semiconductorsubstrate base 101 after selectively, epitaxially growing a type III-Vor a Germanium (Ge) material 122 on top surface 103 of substratematerial 102 in trench 105 between shallow trench isolation (STI)regions 107 and 108. FIG. 1 shows semiconductor substrate or base 101 ofmaterial 102 having top surface 103. Substrate 101 may include, beformed from, deposited with, or grown from silicon, polycrystallinesilicon, single crystal silicon, or various other suitable technologiesfor forming a silicon base or substrate, such as a silicon wafer. Forexample, according to embodiments, substrate 101 may be formed bygrowing a single crystal silicon substrate base material having athickness of between 100 Angstroms and 1000 Angstroms of pure silicon.Alternately, substrate 101 may be formed by sufficient chemical vapordeposition (CVD) of various appropriate silicon or silicon alloymaterials 102 to form a layer of material having a thickness between oneand three micrometers in thickness, such as by CVD to form a thicknessof two micrometers in thickness. It is also considered that substrate101 may be a relaxed, non-relaxed, graded, and/or non-graded siliconalloy material 102. Material 102 may be a relaxed material (e.g., have anon-strained lattice) at surface 103. Material 102 may be a singlecrystal silicon material. Substrate 102 may be made of silicon and havetop surface 103 with a (100) crystal oriented material (e.g., accordingto Miller Index). Substrate 101 may be a “miscut” substrate.

FIG. 1 also shows regions 107 and 108 of shallow trench isolation (STI)material formed or grown on top surface 103 of the substrate 101. STImaterial may be formed of an oxide material or a nitride material orcombination thereof. The STI material may be formed of SiC material oranother STI material as know in the art. The STI material may beamorphous material deposited or grown on material 102 (e.g., at surface103). The STI material may be formed by atomic layer deposition (ALD) orchemical vapor deposition (CVD). The STI material may be deposited viaPlasma Enhanced Chemical Deposition (PECVD). In some cases, any ofvarious oxygen precursors, Silane precursors, or generic precursors canbe used during a process (e.g., PECVD) to form the STI material, as knowin the art. In some cases, the STI material may be formed by a processusing TEOS+O2+RF at 400° C.

In some cases, the bottom surface of regions 107 and 108 may have thesame crystal lattice size as that of material 102 (e.g., at surface103). The STI material may be a relaxed material (e.g., have anon-strained lattice) with respect to its interface (e.g., where it ischemically or atomically bonded to the surface below) with surface 103.

Regions 107 and 108 may have inner STI sidewalls 113 and 115 that definetrench walls of trench 105 having height H1, width W1 and length L1 (notshown, but extending into the page). Trench sidewalls 113 and 115 may bevertical sidewalls that are perpendicular to (e.g., forming an angle ofninety degrees with respect to) substrate surface 103. More specificallytrench 105 may be defined by or have a side at sidewall 113 of region107; a side at sidewall 115 of region 108; a bottom at (or being) topsurface 103 (having W1 and L1); a top at upper opening 140 (having W1and L1); and top corners 111 and 112 (e.g., upper opening cornersextending Length L1) adjacent to top surfaces 116 and 117 of regions 107and 108.

Regions 107 and 108 may be formed (e.g., thus forming trench 105) bypatterning and etching as known in the art. This may include forming ablanket layer of STI material on surface 103, then patterning andetching the STI material to form STI regions 107 and 108. In some cases,patterning and etching the STI material to form the STI regions includesusing a resist or hard mask underneath a resist for the patterningmaterials. In some cases 1, 2, or 3 resist layers may be used for thepatterning materials. In some cases, patterning and etching the STImaterial to form the STI regions includes using an O2 or O2/Ar plasmaetch at pressures in the 10-100 mTorr range, and at room temperature.Such patterning and etching may also include etching an oxides includingSTI material, by etching with fluorocarbons (e.g., CF4 and/or C4F8), O2and Ar, at pressures in the 10-100 mTorr range, and at room temperature.

Length L1 may be a length of between 10 and 100 nanometers (nm). In somecases L1 is approximately 25 nm. In some cases L1 is equal to (orapproximately the same as) W1. In some cases L1 is greater than or lessthan W1. In this case, the top perspective area formed by top shape 124(e.g., dependent or based upon W1 and L1) may be a rectangle. OptionallyL1 may be equal to W1. In this case, the top perspective area formed bytop shape 124 (e.g., dependent or based upon W1 and L1) may be square.In some cases, the top perspective area formed by top shape 124 isdescribed as a “pyramidal” shape, such as having 4 angled sides thatextend vertically in triangular shapes to form a point. In some cases,the top perspective area formed by top shape 124 does not have acircular or oval shape. In some cases, L1 is a width of between 50 and250 nanometers (nm). In some cases L1 is two times the pitch of thegates of transistor devices formed in the sidewalls of the deviceportions, such as two times the pitch between the gates of transistordevices formed in the sidewalls of the device portions.

According to embodiments H1 of trench 105 may be larger than the L1 ofthe trench such that ratio H1/L1 is >=1.5. In some cases, the ratioH1/L1 is=1.5. In some cases, the ratio H1/L1 is >=2.0. In some cases,the ratio H1/L1 is=2.0. According to some embodiments, W1 may be between10 and 15 nanometers (nm) and H1 may be 350 nanometers (nm).

Epitaxial material 122 may be a selectively grown (e.g., deposited)epitaxial layer of epitaxial material in trench 105. Material 122 may bea selectively, epitaxially grown type III-V or Germanium (Ge) materialgrown from or on top surface 103 of substrate material 102 in trench 105between STI regions 107 and 108. According to some embodiments, material122 may be formed by epitaxial growth (e.g., heteroepitaxy) using atomiclayer epitaxy (ALE), chemical vapor deposition (CVD), Metal-OrganicChemical Vapour Deposition (MOCVD) or Metalorganic vapour phase epitaxy(MOVPE), and may only grow from “seed” surface 103 below trench. In somecases, material 122 may be formed by epitaxial growth (e.g.,heteroepitaxy) using molecular beam epitaxy (MBE), or migration enhancedepitaxy (MEE) and may only grow from “seed” surface 103 below thetrench. Material 122 may be an epitaxially grown crystal buffermaterial, grown from a single crystal Silicon (Si) substrate surface103.

Material 122 is shown having (111) crystal orientation top surfaces 126and 127 forming top surface shape 124, “peak” or crystal growth patternthat results from selectively, epitaxially growing crystaline material122 on or from the (100) crystal orientation surface 103.

Material 122 is also shown having (111) crystal orientation “vertical”sidewalls 123 and 125 touching (e.g., against or in direct contact with)STI “vertical” sidewalls 113 and 115. In some cases sidewalls 123 and125 are parallel to (e.g., form an angle of zero degrees with) STIsidewalls 113 and 115. However, since material 122 is grown from the(100) crystal orientation surface 103, the growth of sidewalls 123 and125 at the edge of material 122 occurs with a (I 11) crystalorientation. Thus, the crystal orientation of sidewalls 123 and 125 isnot stabilized with respect to the vertical wall orientation ofsidewalls 113 and 115, causing crystaline defects in material 122,including crystaline defects along sidewalls 123 and 125 (e.g., see thefive sources of crystaline defects noted below). Thus, device materialformed on or from material 122 may include crystal lattice defects thecause slower or decreased performance, reduced yield, and variationissues in circuit devices built on a device layer.

According to embodiments, five “sources” of defects (e.g., crystallattice defects) may be observed to originate during such a selectiveepitaxial growth process. In some cases, the 5 sources mostly generatesimilar types of defects (threading dislocations, stacking faults, etc.)in the crystal lattice structure of the material. An example where suchdefects exist may include an embodiment where the growth of material 122in trench 105 as shown in and described for FIG. 1, and where H1 is <1.5W1, or H1 is <1.5 L1 (e.g., but otherwise using the dimensions asdescribed above for FIG. 1), or where material 122 is not grown toheight H1. A first source of defect may be referred to as “Stage IIStrain Relaxation” source defects. This defect may include threadingdislocations and similar sources of defects, as know in the art. Asecond source of defect may be described as “Stage III Island Merging”source defects. This defect may include threading dislocations andstacking faults, and similar sources of defects, as know in the art. Athird source of defect may be described as “facets or roughness onsilicon substrate” source defects. This source of defect may includethreading dislocations and stacking faults, and the like, as known inthe art. A fourth source of defect may be described as “single atomicsteps on a silicon substrate” source defects. This may includeanti-phase boundaries, and the like, as known in the art. A fifth sourceof defect may be described as “epitaxial collision with oxide sidewalls”source defects. This source of defect may include stacking faults,micro-twins, and/or dislocation, and the like source of defects, asknown in the art. Dislocations may include line defects such as havingan extra half plane or missing and extra half plane of the lattice in aline of atoms. Dislocations may be a one-dimensional defect or a linedefect; and may have a three-dimensional influence (e.g., strain fields)on the crystal structure. Stacking faults may include a disruption ordislocation at the edge of stacks of layers of different types of atomsas know in the art. Stacking faults may also include a disruption of theorder or sequence of the layers of different types of atoms. Stackingfaults may be two-dimensional or planar defects as know in the art; andmay have a three-dimensional influence (e.g., strain fields) on thecrystal structure. Micro-twins may include V shaped or two-dimensionalfaults or planar defects as know in the art; and may have athree-dimensional influence (e.g., strain fields) on the crystalstructure.

According to embodiments, the first three sources of defects can betrapped or prevented by a structure or process that uses the concept ofaspect ratio trapping (ART) where Height (H) of the trench (or the finof epitaxially grown material) is larger than the width (W). In somecases, the first three sources of defects can be trapped or prevented byusing a trench having an aspect ratio (height/width and height/length)greater than 1.5. However this scheme leaves large number of defectspropagating towards the device layers in the long direction of the fin.According to embodiments, such defects can be avoided by traping defectsalong the sidewall of the STI forming the trenches (e.g., in both the Wan length L directions) by making the Height (H) of the trench largerthan the width (W) and length (L) of the trench such that ratiosH/W>=1.5 and H/L>=1.5. This ratio may give a minimum H/W ratio limit toblock many defects (e.g., sources 1-3) within a buffer layer formedwithin the trench. An example of this may include continuing the growthof material 122 in trench 105 as shown in and described for FIG. 1, togrow material 122 (e.g., sidewalls 123 and 125) up to or above heightH1, where H1/W1>=1.5 and H1/L1>=1.5 such as described above for FIG. 1.

It is not believed that there was a previous solution to prevent thefifth source of defect that originates at the sidewall of the STI. Forinstance, the fifth source of sidewall defects (epitaxial growthcollision with oxide side walls or trench sidewalls) may not beprevented by ART, alone. In some cases, the root cause for the fifthsource of defect is mechanical obstruction of the (111) growth faces ofthe epitaxial material, STI oxide sub vertical sidewalls of the trench.In this case the side walls may be an amorphous material that forms anon zero angle with the (111) surface of the epitaxially grown material.In one example, this defect may be due to selective epitaxial growth of(111) type material 122 from surface 103 that touches or grows againstsidewalls 113 and 115, as shown in FIG. 1.

According to embodiments, the fifth source of sidewall defects(selective epitaxial growth collision with oxide side walls or trenchsidewalls) may be prevented by selectively, epitaxially growing a typeIII-V or a Germanium (Ge) material (e.g., a “buffer” material) on a topsurface of a substrate material (1) in a trench having sloped sidewalls,such as at an angle of between 40-70 degrees (e.g., 55°) with respect tothe substrate surface (e.g., see FIGS. 2 and 3); and/or (2) in acombined trench having an upper trench over and surrounding the openingof a lower trench (e.g., the lower trench may have the sloped sidewalls,short vertical walls, or tall vertical walls) (e.g., see FIGS. 3-5). Insome cases, the selective epitaxial growth is made or caused in (2)above to develop (110) crystal type sidewalls and grow laterally in theupper trench so it does approach the trench sidewall at zero degrees.Either solution may reduce or prevent the fifth source of sidewalldefect, such as defects due to selective epitaxial growth of (111) typematerial 122 from surface 103 that touches or grows against sidewalls113 and 115, as shown in FIG. 1 (e.g., where growth of material 122(e.g., sidewalls 123 and 125) does not continue up to or above heightH1, where H1/W1>=1.5 and H1/L1>=1.5.

In addition, if the upper trench or lower trench uses the concept ofaspect ratio trapping (ART), the combined trench may also trap, reduceor prevent the first, second, and third source of defects (e.g., seeFIGS. 3-5). For some embodiments, there is a distinction between howsome FIG. 3 and FIG. 4 structures are going to work. For someembodiments, for FIG. 3, the bottom trench will prevent defect source#5, but will not trap all defects from sources #1-#3 (because a 55degree sloped trench can not have an aspect ratio of 1.5 without closingoff the top of the trench). So here the top trench with aspect ratio 1.5or more may be used (e.g., is required) to trap defects from sources#1-3 that escape from the bottom trench. For some embodiments, for FIG.4, the bottom trench will trap all defects from sources #1-3, but source#5 will get created. Here, source #5 may be blocked in the top trench.

Thus, the devices, structures and processes described herein may avoidthe first, second, third and fifth source of crystaline defects notedabove that are due to lattice mismatch in the layer interfaces ofselective epitaxial growth. They may avoid those defects at the topsurfaces of the buffer material of upon which a “device” material, layeror fin(s) may be grown. For example, crystaline defects in the trenchbuffer material will be prevented at a top surface of that material and,thus, not extend into or not exist in the device epitaxy regions wheredevices are formed (e.g., the upper device material of the regions).Thus, device fins formed or grown from the top surfaces of the buffermaterial may provide electronic device material (e.g., wells andchannels) in which reduced defect or defect free fin based devices maybe formed, thus providing faster or increased performance, increasedyield, and fewer variation issues in circuit devices built on or in thedevice material.

FIG. 2 is a schematic cross section view of a portion of a semiconductorsubstrate base 101 after selectively, epitaxially growing a type III-Vor a Germanium (Ge) material 222 (and 232) on top surface 103 ofsubstrate material 102 in trench 205 between shallow trench isolation(STI) regions 207 and 208 having sloped sidewalls 213 and 215. Similarfeature numbers of FIG. 2 may be the same as those described for FIG. 1.In this case, the fifth source of sidewall defects may be prevented byselectively, epitaxially growing a type III-V or a Germanium (Ge) singlecrystal material on a top surface of a substrate material in trench 205having sloped sidewalls 213 and 215, such as at an angle of between 40degrees and 70 degrees (e.g., such as 55 degrees) with respect to thesubstrate surface 103. The angle of 55 degrees may result from etchingusing an etch (e.g., a wet anisotropic etch) that removes silicon alonglattice planes, thus removing the silicon along a (111) lattice plane.According to embodiments, regions 207 and 208 (e.g., trench 205) may beformed by patterning and etching. More detailed embodiments of processesfor forming trench 205 and sidewalls 213 and 215 is provided below withrespect to FIGS. 7A-D and 9.

This solution may reduce or prevent the fifth source of sidewall defect,such as, defects that result from selective epitaxial growth of (111)type material 122 from surface 103 that touches or grows againstvertical sidewalls 113 and 115, as shown in FIG. 1. In some cases,reduce or prevent the fifth source of sidewall defect for embodimentsdescribed for FIG. 1, includes causing or making the selective epitaxialgrowth to develop (110) crystal type sidewalls and grow laterally in theupper trench so it does approach the trench sidewall at zero degrees.

FIG. 2 shows regions 207 and 208 of shallow trench isolation (STI)material formed or grown on top surface 103 of the substrate 101. STImaterial may be formed of an oxide material or a nitride material orcombination thereof. The STI material may be formed of SiC material oranother STI material as know in the art. The STI material may beamorphous material deposited or grown on material 102 (e.g., at surface103), such as described above for forming STI material of regions 107and 108.

FIG. 2 shows trench 205 defined between STI regions 207 and 208 andsurface 103. In some cases, the bottom surface of regions 207 and 208may have the same crystal lattice size as that of material 102 (e.g., atsurface 103). The STI material may be a relaxed material (e.g., have anon-strained lattice) with respect to its interface (e.g., where it ischemically or atomically bonded to the surface below) with surface 103.

Regions 207 and 208 may have inner STI sidewalls 213 and 215 that definetrench walls of trench 205 having height H2 (from surface 103 to top STIsurfaces 216 or 217), bottom width W2 (e.g., at surface 103), bottomlength L2 (not shown, but extending into the page), upper opening 240(e.g., top) width W3, and upper opening 240 (e.g., top) length L3. Insome cases, W2 and W3 can be in a range between 5 nm and <W1. In someembodiments H2 is 1.5× of W2; or in a range between 8 nm to 1.5×W1.

More specifically trench 205 may be defined by or have a side atsidewall 213 of region 207; a side at sidewall 215 of region 208; abottom at (or being) top surface 103 (having W2 and L2); a top at upperopening 240 (having W3 and L3); and top corners 211 and 212 (e.g., upperopening corners extending Length L3) adjacent to top surfaces 216 and217 of regions 207 and 208. Trench sidewalls 213 and 215 may be slopedor angled sidewalls that form an inward angle of between 40 degrees and70 degrees (e.g., such as 55 degrees) (e.g., towards or into trench 205)with respect to the substrate surface 103. Thus, in some cases, width W3may be=W2−(2*Cosine of 55 degrees*H2); or W3 may=W2−˜3*H2. Length L3 maybe=L2−(2*Cosine of 55 degrees*H2); or L3 may=L2−˜3*H2.

In some cases L2 is equal to (or approximately the same as) W2. In thiscase, the top perspective area formed by W2 and L2 (and W3 and L3) formsa square. In some cases L2 is greater than or less than W2. In thiscase, the top perspective area formed by W2 and L2 (and W3 and L3) formsa rectangle. In some cases, the top perspective area formed by W2 and L2(and W3 and L3) does not have a top perspective circular or oval shape.

Top surface pyramidal shape 234 may extend through trench 205 upperopening 240 having width W3 and length L3. Opening 240 may have a topperspective square or rectangular shape having W3 and a length L3proportional to or based on width W2 and Length L2 at the bottom surface(e.g., exposed surface 103) of trench 205, respectively. In some cases,opening 240 does not have a top perspective circular or oval shape. Insome cases, opening 240 is described as having top corners 211 and 212.

In some cases W2 less than or equal to W1. In some cases W2 is 40, 50,60 or 75 percent of W1. The same relationship may exist between L2 andL1. In some cases W3 is between 3 and 20 nm. In some cases W3 is between5 and 7 nm. In some cases W3 is 20 nm.

Epitaxial material 222 may be a selectively grown (e.g., deposited)epitaxial layer of epitaxial material in trench 205. Material 222 may bea selectively, epitaxially grown type III-V or Germanium (Ge) materialgrown from or on top surface 103 of substrate material 102 in trench 205between STI regions 207 and 208. Material 222 may be epitaxially grownfrom the crystal surface of substrate surface 103. According to someembodiments, material 222 may be formed by epitaxial growth (e.g.,heteroepitaxy) using atomic layer epitaxy (ALE), chemical vapordeposition (CVD), Metal-Organic Chemical Vapour Deposition (MOCVD) orMetalorganic vapour phase epitaxy (MOVPE), and may only grow from “seed”surface 103 below the trench. In some cases, material 222 may be formedby epitaxial growth (e.g., heteroepitaxy) using molecular beam epitaxy(MBE), or migration enhanced epitaxy (MEE) and may only grow from “seed”surface 103 below the trench. Material 222 may be an epitaxially growncrystal buffer material, grown from a single crystal Silicon (Si)substrate surface 103.

In some cases, the choice of (e.g., predetermined) growth conditions formaterial 222 like growth temperature, pressure of gas flux, etc maydefine the selectivity of the epitaxial growth. In some cases, thegrowth of material 222 is grown selectively from surface 103 by choosingor using a predetermined growth temperature range, pressure of gas fluxrange, etc., as known for material 222 to grow from material of surface103, but not grow from or initiate on material of the STI sidewalls ortop surfaces of regions 207 and 208.

According to embodiments, since material 222 is grown from the (100)crystal orientation surface 103, the growth of material 222 begins witha top surface pyrimidal shape 224 having top surfaces 223 and 225 at theedge of material 222 with a (111) crystal orientation. In some cases,top surface pyramidal shape 224 may be replaced with growth forming atop surface flat top or other higher angle planes than (111), such as(311) or even (911) planes. In some cases the choice of (e.g.,predetermined) growth conditions for material 222 like growthtemperature, pressure of gas flux, etc may define or determine the topsurface shape.

In some cases, the choice of (e.g., predetermined) growth conditions fortop surfaces 223 and 225 of material 222 is selected or predetermined totune the process conditions to grow only the (111) planes for topsurfaces 223 and 225, and nothing else (e.g., excluding flat or otherangle planes). However, in other cases, the choice of (e.g.,predetermined) growth conditions for top surfaces 223 and 225 ofmaterial 222 is selected to include or grow flat or other higher angleplanes than (111), such as (311) or even (911) planes.

According to embodiments, since material 222 is grown from the (100)crystal orientation surface 103, the growth of material 222 continues(e.g., during the same growth process or procedure, as material 232)with a top surface pyrimidal shape 234 having top surfaces 233 and 235at the edge of material 222 (e.g., material 232) with a (111) crystalorientation. In some cases, top surface pyramidal shape 234 may bereplaced with growth forming a top surface flat top or other higherangle planes as noted above for shape 224, such as based on the choiceof (e.g., predetermined) growth conditions for material 222. Material232 is shown with top surface pyramidal shape 234 having (111) crystalorientation top surfaces 233 and 235 forming a “peak” or crystal growthpattern above top surfaces 216 and 217 of regions 207 and 208, such asresulting from selectively, epitaxially growing crystaline material 222on or from the (100) crystal orientation surface 103.

In some cases material 232 is the same material as material 222. In somecases material 232 is the same material grown during the same growthprocess as material 222. In some cases material 232 is material 222 asmaterial 222 continues to grown during a single growth process. Material222 and 232 may be a “buffer” material as know in the art, such as amaterial to provide a surface upon which to epitaxially grow a devicelayer or material (e.g., for forming electronic or transistor devices,channels, diffusion layers, gates, etc. . . . ).

Material 232 is shown having (111) crystal orientation top surfaces 233and 235 touching (e.g., impinging upon, disposed against or in directcontact with) STI sidewalls 213 and 215. The (111) crystal orientationof top surfaces 233 and 235 may cause the shape or angle of theirsurface (e.g., their planar surface) to not be constrained or changed bythe material of sidewalls 213 and 215. In some cases sidewalls 233 and235 are parallel to (e.g., form an angle of zero degrees with) STIsidewalls 213 and 215. In some cases, top surfaces 233 and 235 may bedescribed as “sidewalls” since they are touching (e.g., against or indirect contact with) STI sidewalls 213 and 215.

The (111) crystal orientation of sidewalls 233 and 235 may be stabilizedwith respect to the between 40 and 70 degree (e.g., such as 55 degree)sloped vertical wall orientation of sidewalls 213 and 215, preventing oravoiding crystaline defects in material 232, including the fifth sourceof crystaline defects along sidewalls 123 and 125. For example, trenchsidewalls 213 and 215 may form an inward angle of between 40 degrees and70 degrees (e.g., such as 55 degrees) (e.g., towards or into trench 205)with respect to the substrate surface 103. In some cases, trenchsidewalls 213 and 215 may be sloped or angled sidewalls having a slope(e.g., planar surface) that is parallel to or forms an angle of zerodegrees with sidewalls (e.g., (111) crystal planar surface) ofepitaxially grown layer of crystal epitaxial material 232 grown from oron (100) crystal oriented substrate surface 103 in trench 205. In somecases, the epitaxial material has (111) crystal oriented epitaxialmaterial sidewalls 233 and 235 touching (e.g., against or in directcontact with) STI sidewalls 213 and 215. In some cases sidewalls 233 and235 are parallel to (e.g., form an angle of zero degrees with) STIsidewalls 213 and 215.

In some cases, the (111) crystal orientation of sidewalls 233 and 235being stabilized with respect to sidewalls 213 and 215, prevents oravoids the fifth source of sidewall defects because: (1) the epitaxialgrowth does not collide with oxide trench sidewalls; (2) there is nomechanical obstruction of the (111) growth faces of the epitaxialmaterial, STI oxide sub vertical sidewalls of the trench; or (3) thetrench side walls of amorphous material do not form a non zero anglewith the (111) surface of the epitaxially grown material.

For example, the fifth source of crystaline defects in the trench buffermaterial may not extend into or not exist in the device epitaxy regionsor material where devices are formed (e.g., the upper device materialabove material 232). Thus, device fins formed or grown from the topsurfaces of the buffer material may provide electronic device material(e.g., wells and channels) in which reduced defect or defect free finbased devices may be formed, thus providing faster or increasedperformance, increased yield, and fewer variation issues in circuitdevices built on or in the device material.

In some cases, material 222 or 232 is an epitaxial growth of buffermaterial that provides a defect source five free crystalline material orsurface upon which to grow a defect free device material or layer. Thedefect free surface may be surface 244 parallel and in planar alignmentwith top surfaces 216 and 217. In some cases, the defect free surface issurface 244 formed after planarizing material 222, and upon which togrow a defect free device material or layer. In some cases, the defectfree surface is surfaces 233 and 235 extending above surface 244 (e.g.,forming top 234), and upon which to grow a defect free device materialor layer.

In some embodiments, a device layer of device crystal epitaxial materialmay be epitaxially grown on the top surface of the buffer material(e.g., material 232) and lateral growth over a top surface 216 and 217of the first and second STI regions. The lateral growth may createvertical sidewalls of material 232 having (110) crystal orientation(e.g., see FIGS. 3-5). Devices or device fins may be formed from thedevice layer, fins, or fin sidewalls grown from or on material 222 orsurface 233.

FIG. 3 is a schematic cross section view of a portion of a semiconductorsubstrate base 101 after selectively, epitaxially growing a type III-Vor a Germanium (Ge) material on top surface 103 of substrate material102 in a combined trench 350 having an upper trench 306 having a lowersurface above, open to, and surrounding the upper opening of a slopedwalled lower trench 305. Similar feature numbers of FIG. 3 may be thesame as those described for FIGS. 1-2.

In this case, the first, second, third and fifth source of sidewalldefects may be prevented by selectively, epitaxially growing a typeIII-V or a Germanium (Ge) single crystal material on a top surface of asubstrate material in combined trench 350 having upper trench 306 overand surrounding opening 240 of lower trench 305. Specifically, the fifthsource of defect may be prevented by having lower trench 305 having thesloped sidewalls at an angle of between 40 degrees and 70 degrees (e.g.,such as 55 degrees) with respect to the substrate surface (e.g., seeFIG. 2 trench 205); or by using a combined trench concept where uppertrench 306 has an upper trench lower surface 216 and 217 above, open to,and completely surrounding the lower trench upper opening 240. Thefirst, second, third source of sidewall defects may be prevented byhaving the upper trench 306 that use the concept of aspect ratiotrapping (ART), such as by having a trench height at least 1.5 times itswidth and at least 1.5 times its length.

FIG. 3 shows combined trench 350 having an upper trench 306 formedbetween STI regions 307 and 308 and having lower surface (e.g., surfaces216 and 217 and opening 303) above, open to and surrounding upperopening 240 of sloped walled lower trench 305. In some cases, the lowersurface has a width and a length that are greater than a width and alength of opening 240. Upper trench 306 may have lower opening 303 equalto upper opening 240 of lower trench 305 (e.g., both openings havingwidth W3 and length L3). In some cases, opening 303 may be described asthe same opening as opening 240. According to some embodiments, theopenings have the same axis or center (e.g., are horizontally centeredover each other with respect to Width and Length).

For lower trench 305, FIG. 3 shows a schematic cross section view of aportion of a semiconductor substrate base 101 after selectively,epitaxially growing a type III-V or a Germanium (Ge) material 222 (and232) on top surface 103 of substrate material 102 in trench 305 betweenshallow trench isolation (STI) regions 207 and 208 having slopedsidewalls 213 and 215. Lower trench 305 may be similar to trench 205 ofFIG. 2. In some cases, growing material 222 (and 232) on top surface 103of substrate material 102 in trench 305 of FIG. 3 may be similar to thedescriptions above for growing material 222 (and 232) on top surface 103of substrate material 102 in trench 205 in FIG. 2. In this case, thefifth source of defect may be prevented by having lower trench 305having the sloped sidewalls at an angle of between 40 degrees and 70degrees (e.g., such as 55 degrees) with respect to the substrate surface(e.g., see FIG. 2 description).

For upper trench 306, FIG. 3 shows a schematic cross section view of aportion of a semiconductor substrate base 101 after selectively,epitaxially growing a type III-V or a Germanium (Ge) material 322 (and332) from one or more top surfaces of material 232 (or 222, which isgrown from surface 103) in trench 306, and onto top surfaces 216 and 217of STI regions 207 and 208; and grown between STI regions 307 and 308having vertical sidewalls 313 and 315. Features 307, 308, 313, 315, 316and 317 of upper trench 306 may be similar to features 107, 108, 113,115, 116 and 117 of trench 105 of FIG. 1, respectively, with theexception of how they are formed, and any other exceptions noted below.

FIG. 3 shows upper trench STI regions 307 and 308 of STI material formedor grown on top surfaces 216 and 217 of STI regions 207 and 208,respectively. STI material of STI regions 307 and 308 may be formed of asame material as regions 107 and 108. STI material of STI regions 307and 308 may have a same strain characteristics with respect to topsurfaces 216 and 217, as regions 107 and 108 have with respect to topsurface 103.

Regions 307 and 308 may have inner STI sidewalls 313 and 315 that definetrench walls of trench 306 having height H1 (from surface 216 or 217 totop STI surfaces 316 or 317), bottom width W1 (e.g., across surfaces 216or 217, and opening 303), bottom length L1 (not shown, but extendinginto the page), upper opening 340 (e.g., top) width W1, and upperopening 340 length L1. More specifically trench 306 may be defined by orhave a side at sidewall 313 of region 307; a side at sidewall 315 ofregion 308; bottom surfaces 216 and 217, and bottom opening 303; and topsurfaces 316 and 317 of regions 307 and 308. Sidewalk 313 and 315 may bevertical sidewalls that are perpendicular to (e.g., forming an angle ofninety degrees with respect to) surfaces 216 and 217.

According to embodiments, regions 307 and 308 (e.g., trench 306) may beformed by patterning and etching. More detailed embodiments of processesfor forming trenches 305, 306 and 350 and their sidewalls are providedbelow with respect to FIGS. 7A-I and 9.

Growing material 322 (and 332) from one or more top surfaces (e.g., 233and 235, or a planar surface of material 232 adjacent to surfaces 216and 217, see 244 of FIG. 2) of material 232 (or 222, which is grown fromsurface 103) into trench 306 of FIG. 3 may be different than thedescriptions above for growing material 122 on top surface 103 ofsubstrate material 102 in trench 105 in FIG. 1, because material 322 maybe a grown over but not from amorphous top surfaces 216 and 217 of STIregions 207 and 208.

Epitaxial material 322 may be a selectively grown (e.g., deposited)epitaxial layer of epitaxial material in trench 306 that is grown fromtop surfaces 233 and 235 (or a planar surface of material 232 adjacentto surfaces 216 and 217, see 244 of FIG. 2) of material 232 (or 222,which is grown from surface 103) in trench 306, and over amorphous topsurfaces 216 and 217 of STI regions 207 and 208, between verticalsidewalls 313 and 315. Material 322 may be a selectively, epitaxiallygrown type III-V or Germanium (Ge) material grown from or on a topsurface of material 232 extending into trench 306 between STI regions307 and 308. According to some embodiments, material 322 may be formedby epitaxial growth (e.g., heteroepitaxy) using atomic layer epitaxy(ALE), chemical vapor deposition (CVD), Metal-Organic Chemical VapourDeposition (MOCVD) or Metalorganic vapour phase epitaxy (MOVPE), and mayonly grow from “seed” surface 103 below trench 305. In some cases,material 322 may be formed by epitaxial growth (e.g., heteroepitaxy)using molecular beam epitaxy (MBE), or migration enhanced epitaxy (MEE)and may only grow from “seed” surface 103 below trench 305. Material 322may be an epitaxially grown crystal buffer material, grown from a singlecrystal Silicon (Si) substrate surface 103, which is initially grown asmaterial 222, then 232, then 322 during the same growth process orprocessing period or “step”.

Material 322 may grow differently than material 222 or 232, due togrowth of material 322 over but not from amorphous top surfaces 216 and217, as compared to growing material 222 and 232 from crystal topsurface 103. Because material 322 is grown from one or more top surfaces(e.g., 233 and 235, or a planar surface of material 232 adjacent tosurfaces 216 and 217, see 244 of FIG. 2) of material 322 (or 222, whichare both grown from crystal seed layer or surface 103 of material 102),but material 322 is not grown from amorphous top surfaces 216 and 217 ofSTI regions 507 and 508. Because of this, in some cases, material 322forms: (1) vertical (110) crystal oriented sidewalls 326 and 327 alongthe top of surfaces 216 and 217; as well as (2) top surfaces 323 and 325above sidewalls 326 and 327 with a (111) crystal orientation. In somecases, the vertical growth rate of material 322 (e.g., growth of topsurface shape 324 in direction H1) is greater than the horizontal rate(e.g., growth of sidewall 326 plus 327 in direction W1).

In this case, the fifth source of defect may be prevented by usingcombined trench 350 with upper trench 306 having upper trench lower STIsurfaces 216 and 217 above, open at lower opening 303 to, and completelysurrounding lower trench 305 upper opening 240, because material 322(e.g., and 332) is grown from crystal seed layer or surface 103, but isnot grown from amorphous top surfaces 216 and 217. Because of this,material 322 forms vertical (110) crystal oriented sidewalls 336 and 337that touch or grow against sidewalls 313 and 315 as described furtherbelow. In some cases, upper trench 306 having lower surfaces completelysurrounding lower trench 305 upper opening 240 includes STI surfaces 216and 217 extending outward from opening 240 in all directions (e.g., 360degrees with respect to an axis pointing straight up through opening240) along the bottom surface of trench 306. In some cases, completelysurrounding lower trench 305 upper opening 240 includes opening 240being an island in the middle of STI surfaces 216 and 217. In somecases, completely surrounding lower trench 305 upper opening 240includes STI surfaces 216 and 217 forming a square or rectangularperimeter around opening 240 (e.g., viewed from above trench 306)

In some cases, the choice of (e.g., predetermined) growth conditions formaterial 322 are similar to those for material 222. In some cases, thegrowth of material 322 is grown selectively from a top surface ofmaterial 232 by choosing or using a predetermined growth temperaturerange, pressure of gas flux range, etc., as known for material 322 togrow from material 232, but not grow from or initiate on material of theSTI top surfaces 216 and 217, or STI sidewalls 313 and 315 of regions207 and 208. In some cases, growth 322 in top trench 206 has the samecrystal orientation as base substrate material 102, such as having (100)or (001) crystal orientation perpendicular to substrate, which is thesame as the orientation of material 102.

According to embodiments, since material 322 has a crystal orientationgrown from the (100) crystal orientation surface 103, the growth ofmaterial 322 continues with the same crystal orientation as that ofmaterial 102. More specifically, in some cases, material 322 has acrystal orientation grown of (111) as it grows vertically to form topsurfaces 323 and 325. This may be similar to descriptions for growingtop surfaces 233 and 235 (e.g., grow from or on top surfaces 223 and225).

According to embodiments, since material 322 has a crystal orientationgrown from the (100) crystal orientation surface 103, the growth ofmaterial 322, from surfaces of material 232, forms a top surfacepyrimidal shape 324 having top surfaces 323 and 325 at the top ofmaterial 322 with a (111) crystal orientation. In some cases, topsurface pyramidal shape 324 may be replaced with growth forming a topsurface Out top or other higher angle planes than (111), such as (311)or even (911) planes. In some cases the choice of (e.g., predetermined)growth conditions for material 322 like growth temperature, pressure ofgas flux, etc may define or determine the top surface shape. In somecases the choice of (e.g., predetermined) growth conditions for material322 like growth temperature, pressure of gas flux, etc may define ordetermine the top surfaces 323 and 325 growth rate or speed.

In some cases, the choice of (e.g., predetermined) growth conditions fortop surfaces 323 and 325 of material 322 is selected or predetermined totune the process conditions to grow only the (111) planes for topsurfaces 323 and 325, and nothing else (e.g., excluding flat or otherangle planes). However, in other cases, the choice of (e.g.,predetermined) growth conditions for top surfaces 323 and 325 ofmaterial 322 is selected to include or grow flat or other higher angleplanes than (111), such as (311) or even (911) planes.

According to embodiments, since material 322 grows from material 232(e.g., surfaces 233 and 235, or a planar surface of material 232adjacent to surfaces 216 and 217, see 244 of FIG. 2) over or touchingamorphous top surfaces 216 and 217 of STI regions 207 and 208, material322 forms vertical (110) crystal oriented sidewalls 326 and 327 alongthe top of surfaces 216 and 217. More specifically, in some cases, asmaterial 322 grows along edges 230 and 231, it grows with or has a (110)crystal orientation as it grows to form vertical sidewalls 326 and 327.This (110) crystal orientation may be different than the (111) crystalorientation sidewalls 123 and 125 of FIG. 1; and may be different thanthe (111) sidewalls 223 and 225 of FIG. 2. In some cases, the choice of(e.g., predetermined) growth conditions for sidewalls 326 and 327 ofmaterial 322 is selected or predetermined to tune the process conditionsto grow only the (110) planes for sidewalls 326 and 327, and nothingelse (e.g., excluding (110) or other angle planes).

According to embodiments, as the (110) sidewalls 326 and 327 of material322 grow across or along the top of surfaces 216 and 217 towards walls313 and 315 (e.g., in direction W1 and L1), the top surfaces 323 and 325grow from the top, or above sidewalls 326 and 327, towards opening 340(e.g., in direction H1). In some cases the choice of (e.g.,predetermined) growth conditions for material 322 like growthtemperature, pressure of gas flux, etc may define or determine thesidewalls 326 and 327 growth rate or speed. In some cases, the verticalgrowth rate of top surfaces 323 and 325 (e.g., in direction H1) isgreater than the horizontal growth rate of sidewalls 326 and 327 (e.g.,in direction W1). In some cases the vertical rate is at least three timeas fast as the horizontal rate. According to embodiments, the growth ofmaterial 322 continues (e.g., during the same growth process orprocedure, as material 332) with: (1) vertical (110) crystal orientedsidewalls 336 and 337 along the top of surfaces 216 and 217; as well (2)top surfaces 333 and 335 above sidewalls 336 and 337 with a (111)crystal orientation, and forming top surface pyramidal shape 334.

In some cases, top surface pyramidal shape 334 may be replaced withgrowth forming a top surface flat top or other higher angle planes asnoted above for shape 324, such as based on the choice of (e.g.,predetermined) growth conditions for material 322. Material 332 is shownwith top surface pyramidal shape 334 having (111) crystal orientationtop surfaces 333 and 335 forming a “peak” or crystal growth patternabove top surfaces 316 and 317 of regions 307 and 308, such as resultingfrom selectively, epitaxially growing crystallite material 322 on orfrom material 232.

In some cases material 332 is the same material as material 322. In somecases material 332 is the same material grown during the same growthprocess as material 322. In some cases material 332 is material 322 asmaterial 322 continues to grown during a single growth process. In somecases, the choice of (e.g., predetermined) growth conditions formaterial 332 are similar to those for material 222 or material 322.Material 322 and 332 may be a “buffer” material as know in the art, suchas a material to provide a surface upon which to epitaxially grow adevice layer or material (e.g., for forming electronic or transistordevices, channels, diffusion layers, gates, etc. . . . ).

In some cases, because material 332 is grown from one or more topsurfaces (e.g., 323 and 325) and one or more sidewalls (e.g., 326 and327) of material 322 (which are both grown from crystal seed layer orsurface 103 of material 102), but material 322 is not grown fromamorphous top surfaces 216 and 217 of STI regions 207 and 208. Becauseof this, in some cases, material 332 continues to form: (1) vertical(110) crystal oriented sidewalls 336 and 337 along the top of surfaces216 and 217; as well as (2) top surfaces 333 and 335 above sidewalls 336and 337 with a (111) crystal orientation. In some cases, the verticalgrowth rate of material 332 continues to be greater than the horizontalrate.

According to embodiments, growth of material 332 continues with the samecrystal orientation as that of material 102. In some cases, material 332has a crystal orientation grown of (111) as it grows vertically to formtop surfaces 333 and 335. This may be similar to descriptions forgrowing top surfaces 323 and 325 (e.g., grow from or on top surfaces 233and 235).

According to embodiments, the growth of material 332, from surfaces ofmaterial 322, forms a top surface pyrimidal shape 334 having topsurfaces 333 and 335 at the top of material 332 with a (111) crystalorientation, such as described for top surface pyrimidal shape 324having top surfaces 323 and 325 at the top of material 322. Top surfacepyramidal shape 334 may extend through trench 306 upper opening 340. Insome cases, opening 340 does not have a top perspective circular or ovalshape. In some cases, opening 340 is described as having top cornerssimilar to corners 111 and 112.

In some cases the choice of (e.g., predetermined) growth conditions formaterial 332 like growth temperature, pressure of gas flux, etc maydefine or determine the top surfaces 323 and 325 growth rate or speed.In some cases, the choice of (e.g., predetermined) growth conditions fortop surfaces 333 and 335 of material 332 is selected or predetermined totune the process conditions to grow only the (111) planes for topsurfaces 333 and 335, and nothing else (e.g., excluding flat or otherangle planes). However, in other cases, the choice of (e.g.,predetermined) growth conditions for top surfaces 333 and 325 ofmaterial 332 is selected to include or grow flat or other higher angleplanes than (111), such as (311) or even (911) planes.

According to embodiments, since material 332 grows from material 322(e.g., surfaces 326 and 327) over or touching amorphous top surfaces 216and 217 of STI regions 207 and 208, material 332 continues to formvertical (110) crystal oriented sidewalls 336 and 337 along the top ofsurfaces 216 and 217, such as described for sidewalls 326 and 327 ofmaterial 322. In some cases, the choice of (e.g., predetermined) growthconditions for sidewalls 336 and 337 of material 332 is selected orpredetermined to tune the process conditions to grow only the (110)planes for sidewalls 336 and 327, and nothing else (e.g., excluding(110) or other angle planes).

In some cases the choice of (e.g., predetermined) growth conditions formaterial 332 like growth temperature, pressure of gas flux, etc maydefine or determine the sidewalls 336 and 337 growth rate or speedsimilar to that described for growing sidewalls 326 and 327 frommaterial 322. In some cases, this causes the growth of sidewalls 336 and337 to reach surfaces 312 and 315; prior to top surfaces 323 and 325reaching surface 316 and 317 (e.g., a corner of surface 316 and 317).Material 332 of sidewalls 336 and 337 having (110) crystal orientationmay be touching (e.g., against or in direct contact with) STI sidewalls313 and 315. In some cases sidewalls 336 and 337 are parallel to (e.g.,form an angle of zero degrees with) STI sidewalls 313 and 315.

In some cases combined trench 350 or the descriptions above for FIG. 3reduce or prevent the first, second, third and fifth source of sidewalldefects by selectively, epitaxially growing a type III-V or a Germanium(Ge) single crystal material on a top surface 103 of a substratematerial in combined trench 350 having upper trench 306 over andsurrounding opening 240 of lower trench 305 having the sloped sidewalls213 and 215 at an angle of between 40 degrees and 70 degrees (e.g., suchas 55 degrees) with respect to the substrate surface 103. In this case,the fifth source of defect may be prevented by having the lower trenchhaving the sloped sidewalls at an angle of between 40 degrees and 70degrees (e.g., such as 55 degrees) with respect to the substrate surface(e.g., see FIG. 2 description); or by using combined trench 350 withupper trench 306 having upper trench lower STI surfaces 216 and 217above, open at lower opening 303 to, and completely surrounding lowertrench 305 upper opening 240. The first, second, third source ofsidewall defects may be prevented by having upper trench 306 with heightH1 at least 1.5 times width W1 and at least 1.5 times length L1 toprovide aspect ratio trapping (ART), such as noted above for FIG. 1,where material 122 is grown to height H1.

For example, the first, second, third and fifth source of defect may nothave extended into or not exist in the epitaxy regions or material wheredevices are formed (e.g., the upper device material above material 332).Thus, device fins formed or grown from the top surfaces of the buffermaterial may provide electronic device material (e.g., wells andchannels) in which reduced defect or defect free fin based devices maybe formed, thus providing faster or increased performance, increasedyield, and fewer variation issues in circuit devices built on or in thedevice material.

FIG. 4 is a schematic cross section view of a portion of a semiconductorsubstrate base 101 after selectively, epitaxially growing a type III-Vor a Germanium (Ge) material on top surface 103 of substrate material102 in a combined trench 450 having an upper trench 306 having a lowersurface above, open to, and surrounding the upper opening of a tallvertical walled lower trench 405. Similar feature numbers of FIG. 4 maybe the same as those described for FIGS. 1-3. However, there may be someexceptions or differences as explained below.

In this case, the first, second, third and fifth source of sidewalldefects may be prevented by selectively, epitaxially growing a type H1-Vor a Germanium (Ge) single crystal material on a top surface of asubstrate material in combined trench 450 having an upper trench 306over and surrounding opening 240 of “tall” lower trench 408.Specifically, the fifth source of defect may be prevented by using acombined trench concept where the upper trench 306 has an upper trenchlower surface 216 and 217 above, open to, and completely surrounding thelower trench upper opening 240. The first, second, third source ofsidewall defects may be prevented by having the upper trench 306, or“tall” lower trench 405 use the concept of aspect ratio trapping (ART),such as by having a trench height at least 1.5 times its width and atleast 1.5 times its length.

FIG. 4 shows combined trench 450 having an upper trench 306 formedbetween STI regions 307 and 308 and having lower surface (e.g., surfaces216 and 217 and opening 303) above, open to and surrounding upperopening 240 of tall vertical walled lower trench 405. Upper trench 306may have lower opening 303 equal to or the same opening as upper opening240 of lower trench 405 (e.g., both openings having width W3 and lengthL3). According to some embodiments, the openings have the same axis orcenter (e.g., are horizontally centered over each other with respect toWidth and Length).

For lower trench 405, FIG. 4 shows a schematic cross section view of aportion of a semiconductor substrate base 101 after selectively,epitaxially growing a type III-V or a Germanium (Ge) material 222 (and432) on top surface 103 of substrate material 102 in trench 405 betweenshallow trench isolation (STI) regions 407 and 408 having tall verticalsidewalls 413 and 415. Lower trench 405 may be similar to trench 105 ofFIG. 1, but have height H2, width W3 and length L3. In some cases,growing material 222 (and 432) on top surface 103 in trench 405 of FIG.4 may be similar to the descriptions above for growing material 122 ontop surface 103 of substrate material 102 in trench 105 in FIG. 1.Consequently, in some cases, trench 405 may be a smaller version oftrench 105 (e.g., with any exceptions noted herein).

According to some embodiments, features 407, 408, 413, 415, 483, 485,432, 433, 434 and 435 of lower trench 405 may be similar to features107, 108, 113, 115, 123, 125, 122 (similar to 432), 126, 124 and 128 oftrench 105 of FIG. 1, respectively, with the exception of (1) havingheight 112, width W3 and length L3 (e.g., as compared to height H1,width W1 and length L1 of trench 105); and any other exceptions notedbelow.

According to some embodiments, corners 411 and 412 of lower trench 405may be similar to corners 211 and 212 of FIG. 3, respectively, with theexception that each of corners 411 and 412 form an angle of 90 degreesbetween a sidewall of trench 405 and top surfaces 216 and 217, whileeach of corners 211 and 212 form an angle of between 40 degrees and 70degrees (e.g., such as 55 degrees) between the sidewalls and surfaces.More specifically trench 405 may be defined by or have a side atsidewall 413 of region 407; a side at sidewall 415 of region 408; abottom at (or being) top surface 103 (having W3 and L3); a top at upperopening 240 (having W3 and L3); and top corners 411 and 412 (e.g., upperopening corners extending Length L3) adjacent to top surfaces 216 and217 of regions 407 and 408. Trench sidewalls 413 and 415 may be tallvertical (e.g., form a right angle with surface 103) with respect to thesubstrate surface 103. Material 432 may have (111) crystal orientation“vertical” sidewalls 483 and 485 touching (e.g., against or in directcontact with) STI “vertical” sidewalls 413 and 415, similar todescriptions above for sidewalls 123 and 125 touching (e.g., against orin direct contact with) STI “vertical” sidewalls 113 and 115 of FIG. 1.

H2 of trench 405 may be larger than the W3 of the trench such that ratioH2/W3 is >=1.5. In some cases, the ratio H2/W3 is=1.5. In some cases,the ratio H2/W3 is >=2.0. In some cases, the ratio H2/W3 is=2.0.According to some embodiments, W3 may be between 10 and 15 nanometers(nm) and H1 may be 350 nanometers (nm). H2 of trench 405 may be largerthan the L3 of the trench such that ratio H2/L3 is >=1.5. In some cases,the ratio H2/L3 is=1.5. In some cases, the ratio H2/L3 is >=2.0. In somecases, the ratio H2/L3 is=2.0. According to some embodiments, L3 may bebetween 10 and 15 nanometers (nm) and H1 may be 350 nanometers (nm). Insome cases L3 is equal to (or approximately the same as) W3. In somecases L3 is greater than or less than W3.

FIG. 4, shows material 432 extending (e.g., growing) through opening240, which may be similar to material 122 adjacent surfaces 126 and 128FIG. 1. Because of this, in some cases, material 432; sidewalls 433 and435; and top surface pyramidal shape 434, may be similar to material122; sidewalls 126 and 128; and top surface pyramidal shape 124 of FIG.1 (e.g., where material 122 is grown to height H1). In this case, thefirst, second, third source of sidewall defects may be prevented byhaving lower trench 405 with height H2 at least 1.5 times width W3 andat least 1.5 times length L3 to provide aspect ratio trapping (ART),such as noted above for FIG. 1 (e.g., where material 122 is grown toheight H1). For example, the first, second, third source of sidewalldefects may be prevented in material 432 at surfaces 433 and 435 (or aplanar surface of material 432 at or adjacent surfaces 216 and 217) dueto the ART of trench 405 (e.g., H2 being >=105 times W3, and H2being >=105 times L3).

For upper trench 306, FIG. 4 shows a schematic cross section view of aportion of a semiconductor substrate base 101 after selectively,epitaxially growing a type III-V or a Germanium (Ge) material 322 (and332) from one or more top surfaces of material 432 (or 222, which isgrown from surface 103) in trench 306, and onto top surfaces 216 and 217of STI regions 407 and 408; and grown between STI regions 307 and 308having vertical sidewalls 313 and 315.

In some embodiments, materials 322; sidewalls 326, 327; top surfaces 323and 325; and top surface pyramidal shape 324, may be similar in bothFIGS. 3 and 4. This may be because 322 is grown from one or more topsurfaces (e.g., 433 and 435, or a planar surface of material 432adjacent to surfaces 216 and 217, e.g., see 244 of FIG. 2) of material432 (or 222, which are both grown from crystal seed layer or surface 103of material 102) but material 322 is not grown from amorphous topsurfaces 216 and 217 of STI regions 407 and 408. Because of this, insome cases, material 322 forms: (1) vertical (110) crystal orientedsidewalls 326 and 327 along the top of surfaces 216 and 217; as well as(2) top surfaces 323 and 325 above sidewalls 326 and 327 with a (111)crystal orientation. In some cases, the vertical growth rate of material322 (e.g., growth of top surface shape 324 in direction H1) is greaterthan the horizontal rate (e.g., growth of sidewall 326 plus 327 indirection W1).

According to embodiments, the growth of material 322 continues (e.g.,during the same growth process or procedure) as material 332 as notedabove. In some cases, because material 332 is grown from one or more topsurfaces (e.g., 323 and 325) and one or more sidewalls (e.g., 326 and327) of material 322 (which are both grown from crystal seed layer orsurface 103 of material 102), but material 322 is not grown fromamorphous top surfaces 216 and 217 of STI regions 207 and 208. Becauseof this, in some cases, material 332 continues to form: (1) vertical(110) crystal oriented sidewalls 336 and 337 along the top of surfaces216 and 217; and forms a top surface pyrimidal shape 334 having topsurfaces 333 and 335. Material 332 of sidewalls 336 and 337 having (110)crystal orientation may be touching (e.g., against or in direct contactwith) STI sidewalls 313 and 315. In some cases sidewalls 336 and 337 areparallel to (e.g., form an angle of zero degrees with) STI sidewalls 313and 315.

Growing material 322 (and 332) from one or more top surfaces (e.g., 433and 435) of material 432 of FIG. 4 may be different than thedescriptions above for growing material 122 on top surface 103 ofsubstrate material 102 in trench 105 in FIG. 1, because material 322 maybe a grown over but not from amorphous top surfaces 216 and 217 of STIregions 207 and 208. More specifically, in some cases, as material 322grows along edges 230 and 231, it grows with or has a (110) crystalorientation as it grows to form vertical sidewalls 326 and 327 whichtouch sidewalls 313 and 315. Consequently, in these cases, the otherfeatures of trench 306 may be similar to trench 306 (e.g., with anyexceptions noted herein).

In some cases, the fifth source of sidewall defects may not be preventedin material 432 due to trench having the sloped sidewalls at an angle ofbetween 40 degrees and 70 degrees (e.g., such as 55 degrees) withrespect to the substrate surface (e.g., see FIG. 2 description of trench305). However, according to embodiments, the fifth source of sidewalldefects may be prevented in material 432 by using combined trench 450with upper trench 306 having upper trench lower STI surfaces 216 and 217above, open at lower opening 503 to, and completely surrounding lowertrench 405 upper opening 440.

According to embodiments, trenches 405, 306 and 450 and their sidewallsmay be formed by patterning and etching. More detailed embodiments ofprocesses for forming trenches 405, 306 and 450 and their sidewalls isprovided below with respect to FIGS. 8A-I and 10.

Epitaxial material 322 may be a selectively grown (e.g., deposited)epitaxial layer of epitaxial material in trench 306 that is grown fromtop surfaces 433 and 435 of material 432 (or 222, which is grown fromsurface 103) in trench 306, and over amorphous top surfaces 216 and 217of STI regions 207 and 208, between vertical sidewalls 313 and 315, asdescribed above for growing material 322 from surfaces of material 232.Material 322 may be an epitaxially grown crystal buffer material, grownfrom a single crystal Silicon (Si) substrate surface 103, which isinitially grown as material 222, then 432, then 322 during the samegrowth process or processing period or “step”.

In some cases, the choice of (e.g., predetermined growth conditions formaterial 322 are similar to those for material 222. In some cases, thegrowth of material 322 is grown selectively from a top surface ofmaterial 432 by choosing or using a predetermined growth temperaturerange, pressure of gas flux range, etc., as known for material 322 togrow from material 432, but not grow from or initiate on material of theSTI top surfaces 216 and 217, or STI sidewalls 313 and 315 of regions207 and 208.

In some cases combined trench 450 or the descriptions above for FIG. 4reduce or prevent the first, second, third and fifth source of sidewalldefects by selectively, epitaxially growing a type III-V or a Germanium(Ge) single crystal material on a top surface 103 of a substratematerial in combined trench 450 having upper trench 306 over andsurrounding opening 240 of lower trench 405 having “tall” verticalsidewalls 413 and 415 with respect to the substrate surface 103. In thiscase, the fifth source of defect may be prevented by using combinedtrench 450 with upper trench 306 having upper trench lower STI surfaces216 and 217 above, open at lower opening 303 to, and completelysurrounding lower trench 405 upper opening 240. The first, second, thirdsource of sidewall defects may be prevented by (1) having upper trench306 with height H1 at least 1.5 time width W1 and at least 1.5 timelength L1 to provide aspect ratio trapping (ART), such as noted abovefor FIG. 1 (e.g., where material 122 is grown to height H1); or (2)having lower trench 405 with height H2 at least 1.5 time width W3 and atleast 1.5 time length L3 to provide aspect ratio trapping (ART), such asnoted above for FIG. 1 (e.g., where material 122 is grown to height H1).

For example, the first, second, third and fifth source of of crystalinedefects in the trench buffer material may not extend into or not existin the device epitaxy regions or material where devices are formed(e.g., the upper device material above material 332). Thus, device finsformed or grown from the top surfaces of the buffer material may provideelectronic device material (e.g., wells and channels) in which reduceddefect or defect free fin based devices may be formed, thus providingfaster or increased performance, increased yield, and fewer variationissues in circuit devices built on or in the device material.

FIG. 5 is a schematic cross section view of a portion of a semiconductorsubstrate base 101 after selectively, epitaxially growing a type III-Vor a Germanium (Ge) material on top surface 103 of substrate material102 in a combined trench 550 having an upper trench 306 having a lowersurface above, open to, and surrounding the upper opening of a shortvertical walled lower trench 505. Similar feature numbers of FIG. 5 maybe the same as those described for FIGS. 1-4. However, there may be someexceptions or differences as explained below.

In this case, the first, second, third and fifth source of sidewalldefects may be prevented by selectively, epitaxially growing a typeIII-V or a Germanium (Ge) single crystal material on a top surface of asubstrate material in combined trench 550 having upper trench 306 overand surrounding opening 240 of “short” lower trench 505 (e.g., the“short” lower trench having vertical sidewalls having a trench heightless than 1.5 times its width or less than 1.5 times its length).Specifically, the fifth source of defect may be prevented by using acombined trench concept where upper trench 306 has an upper trench lowersurface 216 and 217 above, open to, and completely surrounding the lowertrench upper opening 240. The first, second, third source of sidewalldefects may be prevented by having the upper trench 306 that use theconcept of aspect ratio trapping (ART), such as by having a trenchheight at least 1.5 times its width and at least 1.5 times its length.

FIG. 5 shows combined trench 550 having an upper trench 306 formedbetween STI regions 307 and 308 and having lower surface (e.g., surfaces216 and 217 and opening 303) above, open to and surrounding upperopening 240 of short vertical walled lower trench 505. Upper trench 306may have lower opening 303 equal to or the same opening as upper opening240 of lower trench 405 as noted for FIG. 4.

H3 of lower trench 505 may be larger than the W3 of the trench but theratio H2/W3 is <1.5. In some cases, H3 is less than the W3. H3 of trench505 may be larger than the L3 of the trench but the ratio H2/L3 is <1.5.In some cases, H3 is less than the L3. Trench 505 may be described asnot being an ART trench.

For lower trench 505, FIG. 5 shows a schematic cross section view of aportion of a semiconductor substrate base 101 after selectively,epitaxially growing a type III-V or a Germanium (Ge) material 222 (and532) on top surface 103 of substrate material 102 in trench 505 betweenshallow trench isolation (STI) regions 507 and 508 having short verticalsidewalls 513 and 515. Lower trench 505 may be similar to trench 405 ofFIG. 3, but have height H3, width W3 and length L3. In some cases,growing material 222 (and 532) on top surface 103 in trench 505 of FIG.5 may be similar to the descriptions above for growing material 122 ontop surface 103 of substrate material 102 in trench 105 in FIG. 1 (e.g.,where material 122 is grown to height H1). Consequently, in some cases,trench 505 may be a shorter version of trench 405 (e.g., with anyexceptions noted herein). In some cases, H3 is in a range of between 1nm and <1.5×W3.

According to some embodiments, features 507, 508, 513, 515, 583, 585,532, 533, 534 and 535 of lower trench 505 may be similar to features407, 408, 413, 415, 483, 485, 432, 433, 434 and 435 of lower trench 405of FIG. 3, respectively, with the exception of (1) having height 113(e.g., as compared to height H2 of trench 405); and other exceptionsnoted below. More specifically trench 505 may be defined by or have aside at sidewall 513 of region 507; a side at sidewall 515 of region508; a bottom at (or being) top surface 103 (having W3 and L3); a top atupper opening 240 (having W3 and L3); and top corners 411 and 412adjacent to top surfaces 216 and 217 of regions 507 and 508. Trenchsidewalls 513 and 515 may be short vertical (e.g., form a right anglewith surface 103) with respect to the substrate surface 103. Material532 may have (111) crystal orientation “vertical” sidewalls 583 and 585touching (e.g., against or in direct contact with) STI “vertical”sidewalls 513 and 515, similar to descriptions above for sidewalls 123and 125 touching (e.g., against or in direct contact with) STI“vertical” sidewalls 113 and 115 of FIG. 1.

FIG. 5, shows material 532 extending (e.g., growing) through opening240, which may be similar to material 122 below surfaces 126 and 128FIG. 1. Because of this, material 532; sidewalls 533 and 535; and topsurface pyramidal shape 534, may be similar to material 122 of FIG. 1below height H1, such as where defect sources 1-3 exist. In this case,the first, second, third source of sidewall defects may not be preventedby having lower trench 505 because height H3 is not at least 1.5 timeswidth W3 and is not at least 1.5 times length L3. Thus, trench 505 doesnot provide aspect ratio trapping (ART), such as noted above for FIG. 1(e.g., where material 122 is grown to height H1).

For upper trench 306, FIG. 5 shows a schematic cross section view of aportion of a semiconductor substrate base 101 after selectively,epitaxially growing a type III-V or a Germanium (Ge) material 322 (and332) from one or more top surfaces of material 532 (or 222, which isgrown from surface 103) in trench 306, and onto top surfaces 216 and 217of STI regions 507 and 508; and grown between STI regions 307 and 308having vertical sidewalls 313 and 315.

In some embodiments, materials 322; sidewalls 326, 327; top surfaces 323and 325; and top surface pyramidal shape 324, may be similar in bothFIGS. 4 and 5. This may be because material 322 is grown from one ormore top surfaces (e.g., 533 and 535, or a planar surface of material532 adjacent to surfaces 216 and 217, e.g., see 244 of FIG. 2) ofmaterial 532 (or 222, which are both grown from crystal seed layer orsurface 103 of material 102), but material 322 is not grown fromamorphous top surfaces 216 and 217 of STI regions 507 and 508. Becauseof this, in some cases, material 522 forms: (1) vertical (110) crystaloriented sidewalls 326 and 327 along the top of surfaces 216 and 217; aswell as (2) top surfaces 323 and 325 above sidewalls 326 and 327 with a(111) crystal orientation.

According to embodiments, the growth of material 322 continues (e.g.,during the same growth process or procedure) as material 332 as notedabove. In some cases, because material 332 is grown from one or more topsurfaces (e.g., 323 and 325) and one or more sidewalls (e.g., 326 and327) of material 322 (which are both grown from crystal seed layer orsurface 103 of material 102), but material 322 is not grown fromamorphous top surfaces 216 and 217 of STI regions 207 and 208. Becauseof this, in some, cases, material 332 continues to form: (1) vertical(110) crystal oriented sidewalls 336 and 337 along the top of surfaces216 and 217; and forms a top surface pyrimidal shape 334 having topsurfaces 333 and 335. Material 332 of sidewalls 336 and 337 having (110)crystal orientation may be touching (e.g., against or in direct contactwith) STI sidewalls 313 and 315. In some cases sidewalls 336 and 337 areparallel to (e.g., form an angle of zero degrees with) STI sidewalls 313and 315.

Growing material 322 (and 332) from one or more top surfaces (e.g., 533and 535) of material 532 (or 222, which is grown from surface 103) intotrench 306 of FIG. 5 may be different than the descriptions above forgrowing material 122 on top surface 103 of substrate material 102 intrench 105 in FIG. 1, because material 322 may be a grown over but notfrom amorphous top surfaces 216 and 217 of STI regions 207 and 208. Morespecifically, in some cases, as material 322 grows along edges 230 and231, it grows with or has a (110) crystal orientation as it grows toform vertical sidewalls 326 and 327 which touch sidewalls 313 and 315.Consequently, in these cases, the other features of trench 306 may besimilar to trench 306 (e.g., with any exceptions noted herein).

In some cases, the fifth source of sidewall defects may not be preventedin material 532 due to trench having the sloped sidewalls at an angle ofbetween 40 degrees and 70 degrees (e.g., such as 55 degrees) withrespect to the substrate surface (e.g., see FIG. 2 description of trench305). However, according to embodiments, the fifth source of sidewalldefects may be prevented in material 532 by using combined trench 550with upper trench 306 having upper trench lower STI surfaces 216 and 217above, open at lower opening 303 to, and completely surrounding lowertrench 505 upper opening 240.

According to embodiments, trenches 505, 306 and 550 and their sidewallsmay be formed by patterning and etching. More detailed embodiments ofprocesses for forming trenches 505, 306 and 550 and their sidewalls isprovided below with respect to FIGS. 8A-I and 10. Epitaxial material 322may be a selectively grown (e.g., deposited) epitaxial layer ofepitaxial material in trench 306 that is grown from top surfaces 533 and535 of material 532 (or 222, which is grown from surface 103) in trench306, and over amorphous top surfaces 216 and 217 of STI regions 507 and508, between vertical sidewalls 313 and 315, as described above forgrowing material 322 from surfaces of material 232. Material 322 may bean epitaxially grown crystal buffer material, grown from a singlecrystal Silicon (Si) substrate surface 103, which is initially grown asmaterial 222, then 532, then 322 during the same growth process orprocessing period or “step”.

In some cases, the choice of (e.g., predetermined) growth conditions formaterial 322 are similar to those for material 222. In some cases, thegrowth of material 322 is grown selectively from a top surface ofmaterial 532 by choosing or using a predetermined growth temperaturerange, pressure of gas flux range, etc., as known for material 322 togrow from material 532, but not grow from or initiate on material of theSTI top surfaces 216 and 217, or STI sidewalls 313 and 315 of regions207 and 208.

In some cases combined trench 550 or the descriptions above for FIG. 5reduce or prevent the first, second, third and fifth source of sidewalldefects by selectively, epitaxially growing a type III-V or a Germanium(Ge) single crystal material on a top surface 103 of a substratematerial in combined trench 550 having upper trench 306 over andsurrounding opening 240 of lower trench 505. In this case, the fifthsource of defect may be prevented by using combined trench 550 withupper trench 306 having upper trench lower STI surfaces 216 and 217above, open at lower opening 303 to, and completely surrounding lowertrench 505 upper opening 240. The first, second, third source ofsidewall defects may be prevented by having upper trench 306 with heightH1 at least 1.5 time width W1 and at least 1.5 time length L1 to provideaspect ratio trapping (ART), such as noted above for FIG. 1 (e.g., wherematerial 122 is grown to height H1).

For example, the first, second, third and fifth source of crystalinedefects in the trench buffer material may not extend into or not existin the device epitaxy regions or material where devices are formed(e.g., the upper device material above material 332). Thus, device finsformed or grown from the top surfaces of the buffer material may provideelectronic device material (e.g., wells and channels) in which reduceddefect or defect free fin based devices may be formed, thus providingfaster or increased performance, increased yield, and fewer variationissues in circuit devices built on or in the device material.

FIG. 6 is a schematic top view of a portion of a semiconductor substratebase have combined trenches formed over the base. FIG. 6 showssemiconductor substrate base 101 of material 102 from above afterforming combined trenches 650 over the base.

Combined trenches 650 are shown with upper trench 306 having sidewalls615, lower surface 617, lower opening 303, width W1 and length L1. Insome cases, a bottom surface of trench 306 may be described as lowersurface 617 and lower opening 303.

Trenches 650 or 306 have upper surface 616. Lower trench 605 is shownbelow upper trench 306. Lower trench 605 has sidewalls 613, lowersurface 103, and upper opening 204 with width W3 and length L3.

According to embodiments, combined trenches 650 may be any of combinedtrenches 350, 450 or 550 as described herein. In some cases, uppersurface 616 may be or represent both surface 316 and 317. According toembodiments, sidewalls 615 may be or represent sidewalls 313 and 315. Insome cases, lower surface 617 may be or represent both surface 216 and217. According to embodiments, lower trench 605 may be any of trenches300, 405 or 505 as described herein. According to embodiments, sidewalls613 may be or represent sidewalls 213 and 215, sidewalls 313 and 315,sidewalls 413 and 415, or sidewalls 513 and 515.

According to some embodiments, openings 240 and 303 have the samevertical axis or center (e.g., into the page). In some cases, combinedtrench 650 has upper trench lower surfaces 617 completely surroundingupper opening 240, by extending at least 5 to 10 nm outward from opening240 in all directions. In some cases, upper trench lower surfaces 617completely surrounding opening 240 includes opening 240 being an islandin the middle of surfaces 617. In some cases, upper trench lowersurfaces 617 forming a square (e.g., as shown) or rectangular perimeteraround opening 240.

According to embodiments the structures and embodiments described forFIGS. 2-6 include the STI sidewalls coinciding with or having an innerplanar surfaces in directions (e.g., directions L and W as shown inFIGS. 2-6) along the (110) crystal structure direction of surface 103.In some cases, this includes the embodiments described for FIGS. 2-6including STI sidewalls (e.g., sidewalls 613 and 615) coinciding with orhaving an inner planar surface of the sidewalls in a direction (e.g.,directions L1, L2, L3, W1, W2 and W3) along or parallel to the (110)crystal structure direction of surface 103. In some cases, STI sidewalls613 and 615 coincide with the 110 direction of the substrate, such aswhere the 110 direction includes the entire family of 110 directions(e.g., 011, 101, etc., which may be represented by <110>). In someembodiments, this 110 direction may be represented in materials scienceterminology where a family of directions is designated by use of specialbrackets “< >”, as “<110>”. In these cases, the STI sidewalls 613 and615 are possible (e.g., work) from a patterning point of view (e.g., tocreate between 40 degrees and 70 degrees (e.g., such as 55 degrees)sloped trench sidewalls 213 and 215) and lateral epitaxial growth of the(110) plane point of view (e.g., for the 110 growth front sidewalls 326and 327 to approach the STI sidewalls 313 and 315 at 0-degrees) becausethe STI sidewalls of the trenches coincided exactly with the 110direction of the substrate.

According to embodiments, FIGS. 7A-I may show a process of patterningand etching for forming combined trench 350. According to embodiments,FIGS. 7A-D may show a process of patterning and etching for forming STIregions 207 and 208 to form trench 205 (or lower trench 305). Accordingto embodiments. FIGS. 7E-I may show a process of patterning and etchingfor forming regions 307 and 308 to form upper trench 306; and to formcombined trench 350.

FIG. 7A shows a semiconductor substrate after covering areas of the topsurface of the substrate where trenches are to be formed with a mask;and exposing unmasked areas of the top surface of the substrate next tothe masked areas to a wet chemical etchant that etches the substrateanisotropically to form trenches which have outward sloping between 40degrees and 70 degrees (e.g., such as 55 degrees) sidewalls. FIG. 7Ashows pattern or masks 760-762 formed on (e.g., touching) top surface703 of material 102 of substrate 101. Semiconductor substrate 101,material 102 and top surface 103 may be the same as the description forthose features in FIGS. 1-5. Surface 703 may be similar to surface 103but above surface 103, such as by being at or above height H2 abovesurface 103. In some cases, these masks have width W3 and length L3.These masks may be formed by or of photoresist alone, or aphotoresist/oxide combination; or a photoresist/nitride combination,such as known in the art. This may include patterning by covering areasof Silicon of surface 703 where the trenches are to be formed with masks(e.g., a nitride material), such as masks 760-762.

FIG. 7A also shows trenches 705 and 706 formed by etching surface 103between masks 760-762 with a wet chemical etchant that etches siliconanisotropically. This etching may form sidewalls 712-716 of trenches 705and 706 having a between 40 degrees and 70 degrees (e.g., such as 55degrees) angle with respect to surface 703. This may include selectivelyetching the silicon material (e.g., material 102), with respect to(e.g., not etching) masks 760-762, to remove the silicon material (e.g.,material 102) down to surface 103. This may include etching to formtrenchs by exposing unmasked Silicon surface 703 next to the maskedareas to a wet chemical etchant that etches silicon anisotropically(along preferred lattice planes). In some cases, this includes using apotassium hydroxide etch (anisotropic wet etch of silicon) to result intrenches in silicon which have outward sloping between 40 degrees and 70degrees (e.g., such as 55 degrees) sidewalls (top opening larger thanbottom). The angle of between 40 degrees and 70 degrees (e.g., such as55 degrees) degrees may result from using a wet anisotropic etch thatremoves silicon along lattice planes, thus removing the silicon along a(111) lattice plane.

FIG. 7B shows the semiconductor substrate of FIG. 7A after filling thebetween 40 degrees and 70 degrees (e.g., such as 55 degrees) outwardsloping trenches with shallow trench isolation (STI) material. FIG. 7Bshows trenches 705 and 706 filled in with STI material 704 to a heightabove masks 760-762. STI material 704 may be a blanket layer of STImaterial over touching) all the exposed surfaces above substrate 101.This may include depositing STI material by filling the between 40degrees and 70 degrees (e.g., such as 55 degrees) outward slopingtrenches with isolation-oxide (STI).

FIG. 7C shows the semiconductor substrate of FIG. 7A after removing themasks of the original areas of the top surface of the substrate thatwere covered with the masks to expose the top surface of the substratethere. FIG. 7C shows STI material 704 planarized to a height (e.g.,height H2) to expose surfaces 703 of substrate 101; to expose topsurfaces 216 and 217 of STI material regions 207 and 208 in trenches 705and 706; and to remove masks 760-762.

This may include forming STI regions 207 and 208 by removing the masks760-762 of the original Si areas covered with the masks to expose thesilicon there so that the original Si areas isolate regions 207 and 208of the STI material 704. Polishing or planarizing STI material 704 maybe performed by chemical, physical or mechanical polishing as known inthe art to remove STI material 704 and masks 760-762, to form top planarsurfaces 216 and 217 of new STI isolation-oxide material regions 207 and208.

FIG. 7D shows the semiconductor substrate of FIG. 7A after etching theexposed original areas of the top surface of the substrate usingisotropic etching; thus providing trenches in oxide with between 40degrees and 70 degrees (e.g., such as 55 degrees) inward-slopingsidewalls, with the silicon exposed only at the bottom of the trench.FIG. 7D shows trench 205 (or 305) formed by etching surfaces 703 betweenSTI regions 207 and 208 to remove height H2 to expose or form (e.g.,planar) surface 103 of material 102 using wet (or optionally, dry)isotropic etching (e.g., no preferential etching along crystallographicplanes) to create trench 205 with between 40 degrees and 70 degrees(e.g., such as 55 degrees) inward-sloping sidewalls 213 and 215, andbottom surface 103. This may include selectively etching the siliconmaterial (e.g., material 102), with respect to (e.g., not etching) theSTI material of regions 207 and 208, to remove the silicon material(e.g., material 102) down to surface 103. This trench may have heightH2, bottom width W2 and top width W3 and length L3. This may includeforming trench 205 (or 305) with between 40 degrees and 70 degrees(e.g., such as 55 degrees) inward-sloping sidewalls by etching theexposed Si 703 in the original areas using isotropic etching (nopreferential etching along crystallographic planes), a dry etch may beused here; thus providing trenches 205 (or 305) in oxide with between 40degrees and 70 degrees (e.g., such as 55 degrees) inward-slopingsidewalls 213 and 215, with the silicon 103 exposed only at the bottomof the trench. Such sidewalls may be sidewalls 213 and 215 of STIregions 207 and 208; or may form trench 205 or 305 as described forFIGS. 2-3.

According to embodiments, after FIGS. 7A-D a type III-V or a Germanium(Ge) material may be selectively, epitaxially grown in trench 205 or305, such as described for FIGS. 2-3 (e.g., materials 222 and 232).

According to embodiments, FIGS. 7E-I may show a process of patterningand etching for forming regions 307 and 308 (e.g., trench 306).

FIG. 7E shows the semiconductor substrate of FIG. 7A after filling inthe lower trench having between 40 degrees and 70 degrees (e.g., such as55 degrees) inward-sloping sidewalls with another mask. FIG. 7E showstrench 205 (or 305) filled with a pattern or masks 765 formed on (e.g.,touching) top surfaces 103 of material 102; and surfaces 216 and 216 toa height equal to or above height H1 over surfaces 216 and 216. This mayalso include filling in trench trench 205 or 305 (e.g., trenches asdescribed for FIGS. 2-3). Mask 765 may be a blanket mask over (e.g.,touching) all the exposed surfaces above substrate 101. In some cases,this masks may be formed by or of photoresist alone, or aphotoresist/oxide combination; or a photoresist/nitride combination.This may include deposition of mask material 765 by filling in trench205 having between 40 degrees and 70 degrees (e.g., such as 55 degrees)inward-sloping sidewalls 213 and 215 between the old STI regions 207 and208 (e.g., formed at FIG. 7D above) with another mask (e.g., a nitridehardmask 765) to a height above the sidewalls and planarizing the mask(e.g., down to height H2 plus H1 above surface 103). Polishing orplanarizing mask 765 may be performed by chemical, physical ormechanical polishing as known in the art to remove mask material 765, toform a top planar surfaces of mask 765.

FIG. 7F shows the semiconductor substrate of FIG. 7A after patterningand etching the new, other mask to form openings to the old STI regions,thus creating larger square mesas of the new mask over the lower trench.FIG. 7F shows pattern or masks 766-768 formed on a top surface of mask765, and trenches 721 and 723 etched to expose surfaces 216 and 217 ofregions 207 and 208. In some cases, masks 766-768 have width length L1.Masks 766-768 may be formed by or of photoresist alone, or aphotoresist/oxide combination; or a photoresist/nitride combination.This may include patterning and etching to form trenches 721 and 723 bylithographically patterning and etching the new mask 765 to formopenings 721 and 723 to STI regions 207 and 208, thus creating largersquare mesas of mask 765 (larger than the lower trench width W2) of thenew mask 765 over the lower trench 205.

FIG. 7G shows the semiconductor substrate of FIG. 7A after filling theopenings to the old STI regions with shallow isolation-oxide (STI)material. FIG. 7G shows trenches 721 and 723 filled with STI material775 on (e.g., touching) surfaces 216 and 216 to a height equal to orabove height H1 over surfaces 216 and 216. STI material 775 may be ablanket STI material over (e.g., touching) all the exposed surfacesabove substrate 101. This may include depositing STI material to filltrenches 721 and 723 by filling the openings to STI regions 207 and 208with new isolation-oxide (STI) 775.

FIG. 7H shows the semiconductor substrate of FIG. 7A after polishing thenew STI isolation-oxide to expose the larger square mesas of the new,other mask and the new oxide/STI in the openings to the old STI regions.FIG. 7H shows STI material 775 planarized to a height (e.g., height H1)to expose mask 765; to create expose top surfaces 316 and 317 of STImaterial regions 307 and 308 in trench 306; and to remove masks 766-768.This may include forming STI regions 307 and 308 by polishing theisolation-oxide 775 to (1) expose the larger square mesas 765 of thenew, other mask 765 (e.g., nitride) over the lower trench 405, (2)expose surfaces 316 and 317 of oxide in the openings 721 and 732 to STIregions 207 and 208, thus forming regions 307 and 308 of the STImaterial 775. Polishing or planarizing STI material 775 may be performedby chemical, physical or mechanical polishing as known in the art toform top planar surfaces 316 and 317 of new STI isolation-oxide materialregions 307 and 308.

FIG. 7I shows the semiconductor substrate of FIG. 7A after selectivelyetching or removing the larger square mesas of the new, other mask overthe lower trench (e.g., nitride) without removing any new oxide, so thatthe new oxide in the openings to the old STI regions remains; thusproviding an upper trench in oxide with vertical sidewalls and having alower opening over and surrounding an upper opening of a lower trenchhaving between 40 degrees and 70 degrees (e.g., such as 55 degrees)inward-sloping sidewalls. FIG. 7I shows trenches 306 and 305 (e.g.,fomed from trench 205) which may be formed by selectively etching maskmaterial 765 with respect to material of STI regions 207, 208, 307 and308, and substrate material 102; to create or expose trenches 306 and305 of combined trench 350. Trenches 306 and 305 may be formed byetching to form them separately or simultaneously (e.g., trench 305 isformed during the same etch process or as an immediate chemical etchingcontinuation of etching to form trench 306).

Trenches 306 and 305 may be formed by etching surfaces of mask 765regions between STI regions 207, 208, 307 and 308 using wet (oroptionally, dry) isotropic etching (e.g., no preferential etching alongcrystallographic planes). This etching may remove height H1 of mask 765to expose or form top (e.g., planar) surfaces 216 and 217 of regions 207and 208, and openings 303 and 240, to create trench 306 with verticalsidewalls 313 and 315. This etching may also remove height H2 of mask765 to expose or form top (e.g., planar) surface 103 of material 102, tocreate trench 305 with between 40 degrees and 70 degrees (e.g., such as55 degrees) inward-sloping sidewalls 213 and 215, and bottom surface103. This may include selectively etching the mask 765 material withrespect to (e.g., not etching) the STI material of regions 207, 208, 307and 308, to remove the mask 765 down to surface 103. In some cases, thismay include selectively etching the mask 765 material with respect tomaterial 102. Such etching may include etching the exposed etching themask 765 material using wet (or optionally dry) isotropic etching (nopreferential etching along crystallographic planes). Etching to formtrench 306 may include forming trench 306 by selectively etching orremoving the larger square mesas 765 of the new mask 765 (e.g., nitride)over the lower trench 205 without removing any oxide of regions, so thatthe oxide in the openings to STI regions 207 and 208 remains; thusproviding upper trench 306 in oxide regions 307 and 308 (with verticalsidewalls 313 and 315) over and surrounding upper opening 240 of slopedwalled lower trench 305. The upper trench 306 may have height H1, bottomwidth W1 and length L1, where height H1 is >=1.5 times W1 and >=1.5times L1 such as described above for FIG. 1.

Trench 306 sidewalls may include sidewalls 313 and 315 of STI regions307 and 308; or may form trench 306 as described for FIGS. 3-5.According to embodiments, after FIGS. 7A-I a type III-V or a Germanium(Ge) material may be selectively, epitaxially grown in combined trench350, such as described for FIG. 3 (e.g., materials 222, 232, 322 and332).

According to embodiments, FIGS. 8A-I may show a process of patterningand etching for forming combined trench 450 or 550. According toembodiments, FIGS. 8A-D may show a process of patterning and etching forforming STI regions 407 and 408 to form lower trench 405. In some cases,FIGS. 8A-D may show a process of patterning and etching for forming STIregions 507 and 508 to form lower trench 505. According to embodiments,FIGS. 8E-I may show a process of patterning and etching for formingregions 307 and 308 to form upper trench 306; and to form combinedtrench 450 or 550.

FIG. 8A shows a semiconductor substrate after covering areas of the topsurface of the substrate where trenches are to be formed with a mask;and exposing unmasked areas of the top surface of the substrate next tothe masked areas to a dry chemical etchant that etches the substrateanisotropically to form trenches which have vertical sidewalls. FIG. 8Ashows pattern or masks 760-762 formed on (e.g., touching) top surface703 of material 102 of substrate 101. Semiconductor substrate 101,material 102 and top surface 103 may be the same as the description forthose features in FIGS. 1-5. Surface 703 may be similar to surface 103but above surface 103, such as by being at or above height H2 abovesurface 103. In some cases, these masks have width W3 and length L3.These masks may be formed by or of photoresist alone, or aphotoresist/oxide combination; or a photoresist/nitride combination,such as known in the art. This may include patterning by covering areasof Silicon of surface 703 where the trenches are to be formed with masks(e.g., a nitride material), such as masks 760-762.

FIG. 8A also shows trenches 805 and 806 formed by etching surface 103between masks 760-762 with a dry chemical etchant that etches siliconanisotropically. This etching may form vertical sidewalls 812-816 oftrenches 805 and 806 having a 90 degree angle with respect to surface703. This may include selectively etching the silicon material (e.g.,material 102), with respect to (e.g., not etching) masks 760-762, toremove the silicon material (e.g., material 102) down to surface 103.This may include etching to form trenchs by exposing unmasked Siliconsurface 703 next to the masked areas to a dry chemical etchant thatetches silicon anisotropically (along preferred lattice planes). In somecases, this includes using a Chlorine or another acidic dry chemistry(anisotropic dry etch of silicon) to result in trenches in silicon whichhave vertical sidewalls. In some cases, other such chemistries mayinclude a “halogen” to in place of or to supplement the Chlorine. Such ahalogen may include Fluorine; or combinations of Clorine and Fluorine.

FIG. 8B shows the semiconductor substrate of FIG. 8A after filling thevertical sidewall trenches with shallow trench isolation (STI) material.FIG. 8B shows trenches 805 and 806 filled in with STI material 804 to aheight above masks 760-762. STI material 804 may be a blanket layer ofSTI material over (e.g., touching) all the exposed surfaces abovesubstrate 101. This may include depositing STI material by fillingvertical sidewall trenches with isolation-oxide (STI).

FIG. 8C shows the semiconductor substrate of FIG. 8A after removing themasks of the original areas of the top surface of the substrate thatwere covered with the masks to expose the top surface of the substratethere. FIG. 8C shows STI material 804 planarized to a height (e.g.,height H2) to expose surfaces 703 of substrate 101; to expose topsurfaces 216 and 217 of STI material regions 407 and 408 in trenches 805and 806: and to remove masks 760-762.

This may include forming STI regions 407 and 408 by removing the masks760-762 of the original Si areas covered with the masks to expose thesilicon there so that the original Si areas isolate regions 407 and 408of the STI material 804. Polishing or planarizing STI material 804 maybe performed by chemical, physical or mechanical polishing as known inthe art to remove STI material 804 and masks 760-762, to form top planarsurfaces 216 and 217 of new STI isolation-oxide material regions 407 and408.

FIG. 8D shows the semiconductor substrate of FIG. 8A after etching theexposed original areas of the top surface of the substrate usingisotropic etching; thus providing trenches in oxide with verticalsidewalls, with the silicon exposed only at the bottom of the trench.FIG. 8D shows trench 405 formed by etching surfaces 703 between STIregions 407 and 408 to remove height H2 to expose or form (e.g., planar)surface 103 of material 102 using wet (or optionally, dry) isotropicetching (e.g., no preferential etching along crystallographic planes) tocreate trench 405 with vertical sidewalls 413 and 415, and bottomsurface 103. This may include selectively etching the silicon material(e.g., material 102), with respect to (e.g., not etching) the STImaterial of regions 407 and 408, to remove the silicon material (e.g.,material 102) down to surface 103. This may include forming trench 405with vertical sidewalls by etching the exposed Si 703 in the originalareas using isotropic etching (no preferential etching alongcrystallographic planes), a dry etch may be used here; thus providingtrench 405 in oxide with vertical sidewalls 413 and 415, with thesilicon 103 exposed only at the bottom of the trench. Such sidewalls maybe sidewalls 413 and 415 of STI regions 407 and 408; or may form trench405 as described for FIG. 4. This trench may have height H2, and widthW3 and length L3, where height H2 is >=1.5 times W3 and >=1.5 times L3such as described above for FIG. 4.

According to embodiments, after FIGS. 8A-D a type III-V or a Germanium(Ge) material may be selectively, epitaxially grown in trench 405, suchas described for FIG. 4 (e.g., materials 222 and 432).

According to embodiments, STI regions 507 and 508 having height H3 canbe formed in FIGS. 8A-D to form trench 405 as described for FIG. 5,instead of forming STI regions 407 and 408 having height 1-12 asdescribed in FIGS. 8A-D. This embodiment may include the descriptionsabove for FIGS. 8A-D but having the trench 505 fomed with height H3,instead of trench 405 formed with height H2, as described for FIGS. 4-5.This trench may have height H3, and width W3 and length L3, where heightH2 is <1.5 times W3 and <1.5 times L3 such as described above for FIG.5. Also, for this embodiment, according to embodiments, after FIGS. 8A-Da type III-V or a Germanium (Ge) material may be selectively,epitaxially grown in trench 505, such as described for FIG. 5 (e.g.,materials 222 and 532).

According to embodiments, FIGS. 8E-I may show a process of patterningand etching for forming regions 307 and 308 (e.g., trench 306). Thesedescriptions may be similar to the descriptions above for figures FIGS.7E-I, but FIGS. 8E-I may form trench 306 above trench 405 or 505, suchas described for FIG. 4 or 5.

For example, FIG. 8E shows the semiconductor substrate of FIG. 8A afterfilling in the lower trench having vertical sidewalls with another mask,such as described for FIG. 7E filling in trench 205 (or 305) filled witha pattern or masks 765 formed on (e.g., touching) top surfaces 103 ofmaterial 102; and surfaces 216 and 216 to a height equal to or aboveheight H1 over surfaces 216 and 216. This may also include filling intrench trench 405 or 505 (e.g., trenches as described for FIGS. 4-5).

FIG. 8F shows the semiconductor substrate of FIG. 8A after patterningand etching the new, other mask to form openings to the old STI regions,thus creating larger square mesas of the new mask over the lower trench.

FIG. 8G shows the semiconductor substrate of FIG. 8A after filling theopenings to the old STI regions with shallow isolation-oxide (STI)material.

FIG. 8H shows the semiconductor substrate of FIG. 8A after polishing thenew STI isolation-oxide to expose the larger square mesas of the new,other mask and the new oxide/STI in the openings to the old STI regions.

FIG. 8I shows the semiconductor substrate of FIG. 8A after selectivelyetching or removing the larger square mesas of the new, other mask overthe lower trench (e.g., nitride) without removing any new oxide, so thatthe new oxide in the openings to the old STI regions remains; thusproviding an upper trench in oxide with vertical sidewalls and having alower opening over and surrounding an upper opening of the lower trench.

FIG. 8I shows trenches 306 and 405 which may be formed by selectivelyetching mask material 765 with respect to material of STI regions 407,408, 307 and 308, and substrate material 102; to create or exposetrenches 306 and 405 of combined trench 350. Trenches 306 and 405 may beformed by etching to form them separately or simultaneously (e.g.,trench 405 is formed during the same etch process or as an immediatechemical etching continuation of etching to form trench 306). This maybe done by etching surfaces of mask 765 regions between STI regions 407,408, 307 and 308 using wet (or optionally, dry) isotropic etching (e.g.,no preferential etching along crystallographic planes) similar todescriptions above in FIG. 7I for forming trenches 306 and 305 byetching surfaces of mask 765 regions between STI regions 207, 208, 307and 308. This etching may also remove height H2 of mask 765 to expose orform top (e.g., planar) surface 103 of material 102, to create trench405 with vertical sidewalls 413 and 415, and bottom surface 103.

According to embodiments, after FIGS. 8A-I a type III-V or a Germanium(Ge) material may be selectively, epitaxially grown in trench 450 or550, such as described for FIGS. 4-5 (e.g., materials 222, 432, 322 and332 for trench 450; or materials 222, 532, 322 and 332 for trench 550).

FIG. 9 is an example process 900 for forming a trench having between 40degrees and 70 degrees (e.g., such as 55 degrees) inward-slopingsidewalls between STI regions, with a substrate top surface exposed atthe bottom of the trench. FIG. 9 may be an example process for formingtrench 205, 305 or 350 as described for FIGS. 2-3.

Block 910 may include covering areas of Silicon of surface 103 where thetrenches are to be formed with a mask (e.g., a nitride material).

Block 920 may include exposing unmasked Silicon surface 103 next to themasked areas to a wet chemical etchant that etches siliconanisotropically (along preferred lattice planes), such as using apotassium hydroxide etch (anisotropic wet etch of silicon results intrenches in silicon which have outward sloping between 40 degrees and 70degrees (e.g., such as 55 degrees) sidewalls (top opening larger thanbottom).

Block 930 may include filling the between 40 degrees and 70 degrees(e.g., such as 55 degrees) outward sloping trenches with isolation-oxide(STI).

Block 940 may include removing the masks of the original Si areascovered with the masks to expose the silicon there.

Block 950 may include etching the exposed Si in the original areas usingisotropic etching (no preferential etching along crystallographicplanes), a dry etch may be used here; thus providing trenches in oxidewith between 40 degrees and 70 degrees (e.g., such as 55 degrees)inward-sloping sidewalls, with the silicon exposed only at the bottom ofthe trench.

Such sidewalls may be sidewalls 213 and 215 of STI regions 207 and 208;or may form trench 205 or 305 as described for FIGS. 2-3, respectively.

In some embodiments, process 900 stops after block 950, such as to formSTI regions 207 and 208; or trench 205 as described for FIG. 2. In someembodiments, process 900 continues after block 950 to form STI regions207, 208, 307 and 308; or combined trench 350 as described for FIG. 3.

Block 960 may include filling in the lower trench having between 40degrees and 70 degrees (e.g., such as 55 degrees) inward-slopingsidewalls between the old STI regions (e.g., formed at FIG. 7D above)with another mask (e.g., a nitride hardmask) to a height above thesidewalls and planarizing the mask.

Block 970 may include lithographically patterning and etching the newmask to form openings to STI regions 207 and 208, thus creating largersquare mesas (larger than the lower trench W2) of the new mask over thelower trench;

Block 980 may include filling the openings to STI regions 207 and 208with new isolation-oxide (STI).

Block 990 may include polishing the isolation-oxide to expose the largersquare mesas of the new, other mask over the lower trench (e.g.,nitride) and the oxide in the openings to STI regions 207 and 208.

Block 995 may include selectively etching or removing the larger squaremesas of the new mask over the lower trench (e.g., nitride) withoutremoving any oxide, so that the oxide in the openings to STI regions 207and 208 remains; thus providing an upper trench (e.g., trench 306) inoxide with vertical sidewalls and having lower opening 303 over andsurrounding upper opening 240 of sloped walled lower trench 305; andproviding a lower trench (e.g., trench 305) in oxide with between 40degrees and 70 degrees (e.g., such as 55 degrees) inward-slopingsidewalls, with the silicon exposed only at the bottom of the lowertrench. Such sidewalls may be sidewalls 213 and 215 of STI regions 207and 208, and sidewalls 313 and 315 of STI regions 307 and 308; or mayform combined trench 350 as described for FIG. 3.

FIG. 10 is an example process 1000 for forming a trench verticalsidewalls between STI regions, with a substrate top surface exposed atthe bottom of the trench. FIG. 10 may be an example process for formingtrench 450 or 550 as described for FIGS. 4-5.

Block 1010 may include covering areas of Silicon of surface 103 wherethe trenches are to be formed with a mask (e.g., a nitride material).

Block 1020 may include exposing unmasked Silicon surface 103 next to themasked areas to a dry chemical etchant that etches siliconanisotropically (along preferred lattice planes), such as using aChlorine or another acidic dry chemistry (anisotropic dry etch ofsilicon) to result in trenches in silicon which have vertical sidewalls(anisotropic dry etch of silicon results in trenches in silicon whichhave vertical sidewalls (top opening equal to bottom). In some cases,other such chemistries may include a “halogen” to in place of or tosupplement the Chlorine. Such a halogen may include Fluorine; orcombinations of Clorine and Fluorine.

Block 1030 may include filling the vertical sidewall trenches withisolation-oxide (STI).

Block 1040 may include removing the masks of the original Si areascovered with the masks to expose the silicon there.

Block 1050 may include etching the exposed Si in the original areasusing isotropic etching (no preferential etching along crystallographicplanes), a dry etch may be used here; thus providing trenches in oxidewith vertical sidewalls, with the silicon exposed only at the bottom ofthe trench.

According to embodiments, such sidewalls may be sidewalls 413 and 415 ofSTI regions 407 and 408; or may form trench 405 as described for FIG. 4(e.g., having height H2 as described for FIG. 4). According to otherembodiments, such sidewalls may be sidewalls 513 and 515 of STI regions507 and 508; or may form trench 505 as described for FIG. 5 (e.g.,having height H3 as described for FIG. 5).

In some embodiments, process 1000 continues after block 1050 to form STIregions 407, 408, 307 and 308; or combined trench 350 as described forFIG. 4. In some embodiments, process 1000 continues after block 1050 toform STI regions 507, 508, 307 and 308; or combined trench 550 asdescribed for FIG. 5.

Block 1060 may include filling in the lower trench having verticalsidewalls between the old STI regions (e.g., formed at FIG. 8D above)with another mask (e.g., a nitride hardmask) to a height above thesidewalls and planarizing the mask.

Block 1070 may include lithographically patterning and etching the newmask to form openings to STI regions 407 and 408, thus creating largersquare mesas (larger than the lower trench W3) of the new mask over thelower trench;

Block 1080 may include filling the openings to STI regions 407 and 408with new isolation-oxide (STI).

Block 1090 may include polishing the isolation-oxide to expose thelarger square mesas of the new, other mask over the lower trench (e.g.,nitride) and the oxide in the openings to STI regions 407 and 408.

Block 1095 may include selectively etching or removing the larger squaremesas of the new mask over the lower trench (e.g., nitride) withoutremoving any oxide, so that the oxide in the openings to STI regions 407and 408 remains: thus providing an upper trench (e.g., trench 306) inoxide with vertical sidewalls and having lower opening 303 over andsurrounding upper opening 240 of vertical walled lower trench 405; andproviding a lower trench (e.g., trench 405) in oxide with verticalsidewalls, with the silicon exposed only at the bottom of the lowertrench.

In some embodiments, such sidewalls may be sidewalls 413 and 415 of STIregions 407 and 408, and sidewalls 313 and 315 of STI regions 307 and308; or may form combined trench 450 as described for FIG. 4 (e.g.,where the heigh of regions 407 and 408 is H2). In other embodiments,such sidewalls may be sidewalls 513 and 515 of STI regions 507 and 508,and sidewalls 313 and 315 of STI regions 307 and 308; or may formcombined trench 550 as described for FIG. 5 (e.g., where the heigh ofregions 507 and 508 is H3).

In some cases, materials 122, 222, 232, 322, 332, 432, and 532 are eacha layer of InP, GaAs, InGaAs, AlGaAs, InAlAs, GaAsSb, or InP material.In some cases, one of material 122, 222, 232, 322, 332, 432, and 532 isa layer of InP, GaAs, InGaAs, AlGaAs, InAlAs, GaAsSb, or InP material.In some cases, (1) material 122 is a bottom layer of InP or GaAsmaterial; (2) material 232, 432, 532 and 322 are a middle layer ofInAlAs material; and (3) material 332 is a top layer of InGaAs materialor material 332 is a top layer is a stack of 5-50 nm InGaAs/2 nm InP/20nm highly doped InGaAs material (with Indium composition from 53% to100% in InGaAs). In some cases, (1) material 122, 232, 432 are 532 are abottom layer of InP or GaAs material; (2) material 322 is a middle layerof InAlAs material; and (3) material 332 is a top layer of InGaAsmaterial or material 332 is a top layer is a stack of 5-50 nm InGaAs/2nm InP/20 nm highly doped InGaAs material (with Indium composition from53% to 100% in InGaAs).

In some cases, materials 122, 222, 232, 322, 332, 432, and 532 may bedescribed as an “epitaxial region”; or a “stack” of epitaxial layers ormaterials. For some embodiments, forming materials 122, 222, 232, 322,332, 432, and 532 is described as “simultaneously” epitaxially growingthe epitaxial materials, layers or regions. For example,“simultaneously” may describe performing, at the same time, the sameprocesses of forming or growing the same materials in different trenchesor combined trenches (e.g., between STI regions or sidewalls). In somecase, simultaneously epitaxially growing the epitaxial materials maydescribe performing, at the same time, the same processes of forming thematerials multiple trenches on surface 103 as described above.

FIGS. 1-10 show one or two single or combined trenches (e.g., trenches105, 205, 350, 450 and 550) defined between STI regions and surface 103.However it is contemplated that more, similar trenches and STI regionsmay exist on substrate 101, similar to that of the single or combinedtrenches (e.g., trenches 105, 205, 350, 450 and 550), such as at leasthundreds or hundreds of thousands.

In some cases, a “combined trench” may have two or more levels (e.g.,vertically oriented, such as upper v. lower) of trenches that are opento each other (e.g., have lower and upper openings that form an openingbetween them). In some cases, a “combined trench” may have upper (e.g.,top) trench and a lower (e.g., bottom) trench, where the upper trenchhas a lower opening over and surrounding an upper opening of the lowertrench. In some cases, the openings have the same axis or center (e.g.,are horizontally centered over each other with respect to Width andLength).

FIG. 11 illustrates a computing device 1100 in accordance with oneimplementation. The computing device 1100 houses board 1102. Board 1102may include a number of components, including but not limited toprocessor 1104 and at least one communication chip 1106. Processor 1104is physically and electrically connected to board 1102. In someimplementations at least one communication chip 1106 is also physicallyand electrically connected to board 1102. In further implementations,communication chip 1106 is part of processor 1104.

Depending on its applications, computing device 1100 may include othercomponents that may or may not be physically and electrically connectedto board 1102. These other components include, but are not limited to,volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flashmemory, a graphics processor, a digital signal processor, a cryptoprocessor, a chipset, an antenna, a display, a touchscreen display, atouchscreen controller, a battery, an audio codec, a video codec, apower amplifier, a global positioning system (GPS) device, a compass, anaccelerometer, a gyroscope, a speaker, a camera, and a mass storagedevice (such as hard disk drive, compact disk (CD), digital versatiledisk (DVD), and so forth).

Communication chip 1106 enables wireless communications for the transferof data to and from computing device 1100. The term “wireless” and itsderivatives may be used to describe circuits, devices, systems, methods,techniques, communications channels, etc., that may communicate datathrough the use of modulated electromagnetic radiation through anon-solid medium. The term does not imply that the associated devices donot contain any wires, although in some embodiments they might not.Communication chip 1106 may implement any of a number of wirelessstandards or protocols, including but not limited to Wi-Fi (IEEE 802.11family), WiMAX (IEEE 802.16 family), IEEE 802.20, long term evolution(LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE, GSM, GPRS, CDMA, TDMA, DECT,Bluetooth, derivatives thereof, as well as any other wireless protocolsthat are designated as 3G, 4G, 5G, and beyond. Computing device 1100 mayinclude a plurality of communication chips 1106. For instance, a firstcommunication chip 1106 may be dedicated to shorter range wirelesscommunications such as Wi-Fi and Bluetooth and a second communicationchip 1106 may be dedicated to longer range wireless communications suchas GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others.

Processor 1104 of computing device 1100 includes an integrated circuitdie packaged within processor 1104. In some implementations, theintegrated circuit die includes (1) a trench having sloped sidewalls atan angle of between 40 degrees and 70 degrees (e.g., such as 55 degrees)with respect to a substrate surface the trench is formed on; and/or (2)in a combined trench having an upper trench over and surrounding theopening of a lower trench formed on a substrate surface; and a layer ofselectively epitaxially grown buffer material grown from the substratesurface, such as described with reference to FIGS. 1-10. The term“processor” may refer to any device or portion of a device thatprocesses electronic data from registers and/or memory to transform thatelectronic data into other electronic data that may be stored inregisters and/or memory.

Communication chip 1106 also includes an integrated circuit die packagedwithin communication chip 1106. In accordance with anotherimplementation, a package including a communication chip incorporatesone or more capacitors such as described above.

In further implementations, another component housed within computingdevice 1100 may contain a microelectronic package including anintegrated circuit die such as described above.

In various implementations, computing device 1100 may be a laptop, anetbook, a notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a mobile phone, a desktopcomputer, a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player,or a digital video recorder. In further implementations, computingdevice 1100 may be any other electronic device that processes data.

Examples

The following examples pertain to embodiments.

Example 1 is a combined trench for growing a selective epitaxial buffermaterial, the combined trench comprising: a first and a second shallowtrench isolation (STI) region on a substrate surface, the first andsecond STI regions having first and second STI inner sidewalls defininga lower trench, the lower trench having a bottom surface that is thesubstrate surface, the lower trench having a lower trench upper opening;and a third and a fourth STI region on the first and second STI regions,the third and fourth STI regions having third and fourth STI innersidewalls defining an upper trench, the upper trench exposing the lowertrench upper opening and the substrate surface; the upper trench havingan upper trench lower surface above and completely surrounding the lowertrench upper opening.

In Example 2, the subject matter of Example 1 can optionally includewherein the upper trench has a height at least 1.5 times a width and atleast 1.5 times a length of the upper trench; and wherein the third andfourth STI inner sidewalls are perpendicular to the substrate surface.

In Example 3, the subject matter of Example 1 can optionally includefurther comprising: a layer of crystal epitaxial material in the lowertrench and in the upper trench, the crystal epitaxial materialselectively epitaxially grown from the substrate surface but is notgrown from STI top surfaces of the lower trench.

In Example 4, the subject matter of Example 3 can optionally includewherein the layer of crystal epitaxial material is a layer of buffermaterial and further comprising: a device layer of device crystalepitaxial material on a top surface of the buffer material, the devicecrystal epitaxial material selectively epitaxially grown from the topsurface of the buffer material.

In Example 5, the subject matter of Example 3 can optionally includewherein the epitaxial material has (111) crystal index sidewallstouching the first and second STI inner sidewalls; and wherein theepitaxial material has (110) crystal index vertical sidewalls touchingthe third and fourth STI inner sidewalls.

In Example 6, the subject matter of Example 1 can optionally includewherein the first and second STI inner sidewalls form an inward angle ofbetween 40 degrees and 70 degrees with respect to the substrate surface.

In Example 7, the subject matter of Example 1 can optionally includewherein the first and second STI inner sidewalls are perpendicular tothe substrate surface.

Example 8 is a tench for growing a selective epitaxial buffer material,the trench comprising: a first and a second shallow trench isolation(STI) region on a substrate surface, the first and second STI regionshaving a first and second STI inner sidewalls defining a trench having abottom surface that is the substrate surface; the first and second STIinner sidewalls forming an inward angle of approximately 55 degrees withrespect to the substrate surface; and a layer of crystal epitaxialmaterial in the trench, the crystal epitaxial material selectivelyepitaxially grown from the substrate surface.

In Example 9, the subject matter of Example 8 can optionally includewherein the layer of crystal epitaxial material has (111) crystal indexmaterial sidewalls touching the first and second STI inner sidewalls.

In Example 10, the subject matter of Example 8 can optionally includewherein the layer of crystal epitaxial material is a layer of buffermaterial and further comprising: a layer of device crystal epitaxialmaterial on a top surface of the buffer material, the device crystalepitaxial material selectively epitaxially grown from the top surface ofthe buffer material.

Example 11 is a method to form a trench for growing a selectiveepitaxial buffer material, the method comprising: forming first andsecond shallow trench isolation (STI) regions on a substrate surface,the first and second STI regions having first and second STI innersidewalls defining a trench having a bottom surface that is thesubstrate surface; the first and second STI inner sidewalls forming aninward angle of 55 degrees with respect to the substrate surface; andselectively epitaxially growing a layer of crystal epitaxial materialfrom the substrate surface and in the trench.

In Example 12, the subject matter of Example 11 can optionally includewherein the layer of crystal epitaxial material has (111) crystal indexmaterial sidewalls touching the first and second STI inner sidewalls.

In Example 13, the subject matter of Example 11 can optionally includewherein the layer of crystal epitaxial material is a layer of buffermaterial and further comprising: selectively epitaxially growing adevice layer of device crystal epitaxial material from a top surface ofthe buffer material.

Example 14 is a method to form a combined trench for growing a selectiveepitaxial buffer material, the method comprising: forming first andsecond shallow trench isolation (STI) regions on a substrate surface,the first and second STI regions having first and second STI innersidewalls defining a lower trench, the lower trench having a bottomsurface that is the substrate surface, the lower trench having a lowertrench upper opening; and forming third and fourth STI regions on thefirst and second STI regions, the third and fourth STI regions havingthird and fourth STI inner sidewalls defining an upper trench, the uppertrench exposing the lower trench upper opening and the substratesurface; the upper trench having an upper trench lower surface above andcompletely surrounding the lower trench upper opening.

In Example 15, the subject matter of Example 14 can optionally includewherein the upper trench has a height at least 1.5 times a width and atleast 1.5 times a length of the upper trench; and wherein the third andfourth STI inner sidewalls are perpendicular to the substrate surface.

In Example 16, the subject matter of Example 14 can optionally includefurther comprising: selectively epitaxially growing a layer of crystalepitaxial material from the substrate surface, into the lower trench andinto the upper trench; and wherein the layer of crystal epitaxialmaterial is not grown from STI top surfaces of the lower trench.

In Example 17, the subject matter of Example 16 can optionally includewherein the layer of crystal epitaxial material is a layer of buffermaterial and further comprising: a layer of device crystal epitaxialmaterial on a top surface of the buffer material, the device crystalepitaxial material selectively epitaxially grown from the top surface ofthe buffer material.

In Example 18, the subject matter of Example 16 can optionally includewherein the epitaxial material has (111) crystal index sidewallstouching the first and second STI inner sidewalls; and wherein theepitaxial material has (110) crystal index vertical sidewalls touchingthe third and fourth STI inner sidewalls.

In Example 19, the subject matter of Example 14 can optionally includewherein the first and second STI inner sidewalls form an inward angle of55 degrees with respect to the substrate surface.

In Example 20, the subject matter of Example 14 can optionally includewherein the first and second STI inner sidewalls are perpendicular tothe substrate surface.

Example 21 is a system for computing comprising: microprocessor coupledto a memory, the microprocessor having at least one combined trenchhaving: a first and a second shallow trench isolation (STI) region on asubstrate surface, the first and second STI regions having first andsecond STI inner sidewalls defining a lower trench, the lower trenchhaving a bottom surface that is the substrate surface, the lower trenchhaving a lower trench upper opening; a third and a fourth STI region onthe first and second STI regions, the third and fourth STI regionshaving third and fourth STI inner sidewalls defining an upper trench,the upper trench open to the lower trench upper opening and thesubstrate surface; the upper trench having an upper trench lower surfaceabove and completely surrounding the lower trench upper opening; abuffer layer of buffer crystal epitaxial material in the lower trenchand in the upper trench, the buffer crystal epitaxial materialselectively epitaxially grown from the substrate surface but not grownfrom STI top surfaces of the lower trench; a device layer of devicecrystal epitaxial material on a top surface of the buffer material, thedevice crystal epitaxial material selectively epitaxially grown from thetop surface of the buffer material; and a plurality of devices formed infins of the device material.

In Example 22, the subject matter of Example 21 can optionally includewherein the upper trench has a height at least 1.5 times a width and atleast 1.5 times a length of the upper trench: wherein the third andfourth STI inner sidewalls are perpendicular to the substrate surface;wherein the epitaxial material has (110) crystal index verticalsidewalls touching the third and fourth STI inner sidewalls; and whereinone of (a) the epitaxial material has (111) crystal index sidewallstouching the first and second STI inner sidewalls, and (b) the first andsecond STI inner sidewalls form an inward angle of 55 degrees withrespect to the substrate surface.

Example 23 is an apparatus comprising means for performing the method ofany one of examples 11-20.

In the description above, for the purposes of explanation, numerousspecific details have been set forth in order to provide a thoroughunderstanding of the embodiments. It will be apparent however, to oneskilled in the art, that one or more other embodiments may be practicedwithout some of these specific details. The particular embodimentsdescribed are not provided to limit embodiments of the invention but toillustrate it. The scope of the embodiments of the invention is not tobe determined by the specific examples provided above but only by theclaims below. In other instances, well-known structures, devices, andoperations have been shown in block diagram form or without detail inorder to avoid obscuring the understanding of the description. Forexample, while embodiments are described herein with STI inner sidewallsforming an inward angle of between 40 degrees and 70 degrees withrespect to the substrate surface, it is considered that that angle maybe approximately 55 degrees, or in some cases, exactly 55 degrees. Whereconsidered appropriate, reference numerals or terminal portions ofreference numerals have been repeated among the figures to indicatecorresponding or analogous elements, which may optionally have similarcharacteristics.

It should also be appreciated that reference throughout thisspecification to “one embodiment”, “an embodiment”, “one or moreembodiments”, or “different embodiments”, for example, means that aparticular feature may be included in the practice of the embodiments.Similarly, it should be appreciated that in the description variousfeatures are sometimes grouped together in a single embodiment, figure,or description thereof for the purpose of streamlining the disclosureand aiding in the understanding of various inventive aspects. Thismethod of disclosure, however, is not to be interpreted as reflecting anembodiment that requires more features than are expressly recited ineach claim. Rather, as the following claims reflect, inventive aspectsof embodiments that may lie in less than all features of a singledisclosed embodiment. For example, although the descriptions and figuresabove describe forming forming a “combined trench” may having two levels(e.g., 306 and 305, 405 or 505) it is considered that a combined trenchmay have more than two levels (e.g., vertically oriented, such as upperand lower) of trenches that are open to each other (e.g., have lower andupper openings that form an opening between them). Thus, the claimsfollowing the Detailed Description are hereby expressly incorporatedinto this Detailed Description, with each claim standing on its own as aseparate embodiment of the invention.

The invention claimed is:
 1. A combined trench for growing a selectiveepitaxial buffer material, the combined trench comprising: a first and asecond shallow trench isolation (STI) region on a substrate surface, thefirst and second STI regions having first and second STI inner sidewallsdefining first and second lower trench sidewalls of a lower trench, thelower trench having a bottom surface that is the substrate surface, thelower trench having a lower trench upper opening, wherein the first andsecond STI inner sidewalls form an inward angle of 55 degrees withrespect to the substrate surface; and a third and a fourth STI region onthe first and second STI regions, the third and fourth STI regionshaving third and fourth STI inner sidewalls defining third and fourthupper trench sidewalls of an upper trench, the upper trench exposing thelower trench upper opening and the substrate surface; the upper trenchhaving an upper trench lower surface above and completely surroundingthe lower trench upper opening.
 2. The combined trench of claim 1,wherein the upper trench has a height at least 1.5 times a width and atleast 1.5 times a length of the upper trench; and wherein the third andfourth STI inner sidewalls are perpendicular to the substrate surface.3. The combined trench of claim 1, further comprising: a layer ofcrystal epitaxial material in the lower trench and in the upper trench,the crystal epitaxial material selectively epitaxially grown from thesubstrate surface but is not grown from STI top surfaces of the lowertrench.
 4. The combined trench of claim 3, wherein the layer of crystalepitaxial material is a layer of buffer material and further comprising:a device layer of device crystal epitaxial material on a top surface ofthe buffer material, the device crystal epitaxial material selectivelyepitaxially grown from the top surface of the buffer material.
 5. Thecombined trench of claim 3, wherein the epitaxial material has (111)crystal index sidewalls touching the first and second STI innersidewalls; and wherein the epitaxial material has (110) crystal indexvertical sidewalls touching the third and fourth STI inner sidewalls. 6.The combined trench of claim 1, wherein the lower trench has a height atleast 1.5 times a width and at least 1.5 times a length of the lowertrench.
 7. The combined trench of claim 1, wherein the first and secondSTI inner sidewalls lean in towards each other to form the inward angleof 55 degrees as they extend upwards and away from the substratesurface.
 8. A trench for growing a selective epitaxial buffer material,the trench comprising: a first and a second shallow trench isolation(STI) region on a substrate surface, the first and second STI regionshaving first and second STI inner sidewalls defining a first and secondlower trench sidewalls of a trench having a bottom surface that is thesubstrate surface; the first and second lower trench sidewalls formingan inward angle of 55 degrees with respect to the substrate surface; anda layer of crystal epitaxial material in the trench, the crystalepitaxial material selectively epitaxially grown from the substratesurface.
 9. The trench of claim 8, wherein the layer of crystalepitaxial material has (111) crystal index material sidewalls touchingthe first and second STI inner sidewalls.
 10. The trench of claim 9,wherein the layer of crystal epitaxial material is a layer of buffermaterial and further comprising: a layer of device crystal epitaxialmaterial on a top surface of the buffer material, the device crystalepitaxial material selectively epitaxially grown from the top surface ofthe buffer material.
 11. The trench of claim 8, wherein the upper trenchhas a height at least 1.5 times a width and at least 1.5 times a lengthof the upper trench.
 12. The trench of claim 8, wherein the lower trenchhas a height at least 1.5 times a width and at least 1.5 times a lengthof the lower trench.
 13. The trench of claim 8, wherein the first andsecond lower trench sidewalls lean in towards each other to form theinward angle of 55 degrees as they extend upwards and away from thesubstrate surface.
 14. A system for computing comprising: amicroprocessor coupled to a memory, the microprocessor having at leastone combined trench having: a first and a second shallow trenchisolation (STI) region on a substrate surface, the first and second STIregions having first and second STI inner sidewalls defining first andsecond lower trench sidewalls of a lower trench, the lower trench havinga bottom surface that is the substrate surface, the lower trench havinga lower trench upper opening; a third and a fourth STI region on thefirst and second STI regions, the third and fourth STI regions havingthird and fourth STI inner sidewalls defining third and fourth uppertrench sidewalls of an upper trench, the upper trench open to the lowertrench upper opening and the substrate surface; the upper trench havingan upper trench lower surface above and completely surrounding the lowertrench upper opening, wherein the first and second STI inner sidewallsform an inward angle of 55 degrees with respect to the substratesurface; a buffer layer of buffer crystal epitaxial material in thelower trench and in the upper trench, the buffer crystal epitaxialmaterial selectively epitaxially grown from the substrate surface butnot grown from STI top surfaces of the lower trench; a device layer ofdevice crystal epitaxial material on a top surface of the buffermaterial, the device crystal epitaxial material selectively epitaxiallygrown from the top surface of the buffer material; and a plurality ofdevices formed in fins of the device material.
 15. The system of claim14, wherein the upper trench has a height at least 1.5 times a width andat least 1.5 times a length of the upper trench; wherein the third andfourth STI inner sidewalls are perpendicular to the substrate surface;wherein the epitaxial material has (110) crystal index verticalsidewalls touching the third and fourth STI inner sidewalls; and whereinthe epitaxial material has (111) crystal index sidewalls touching thefirst and second STI inner sidewalls.
 16. The system of claim 14,wherein the lower trench has a height at least 1.5 times a width and atleast 1.5 times a length of the lower trench.
 17. A system for computingcomprising: a microprocessor coupled to a memory, the microprocessorhaving at least one combined trench having: a first and a second shallowtrench isolation (STI) region on a substrate surface, the first andsecond STI regions having first and second STI inner sidewalls defininga first and second lower trench sidewalls of a trench having a bottomsurface that is the substrate surface; the first and second lower trenchsidewalls forming an inward angle of 55 degrees with respect to thesubstrate surface; and a layer of crystal epitaxial material in thetrench, the crystal epitaxial material selectively epitaxially grownfrom the substrate surface.
 18. The system of claim 17, wherein thelayer of crystal epitaxial material in the trench is a buffer layer ofbuffer crystal epitaxial material selectively epitaxially grown from thesubstrate surface but not grown from STI top surfaces of the lowertrench; further comprising: a device layer of device crystal epitaxialmaterial on a top surface of the buffer material, the device crystalepitaxial material selectively epitaxially grown from the top surface ofthe buffer material; and a plurality of devices formed in fins of thedevice material.
 19. The system of claim 17, wherein the lower trenchhas a height at least 1.5 times a width and at least 1.5 times a lengthof the lower trench.
 20. The system of claim 17, wherein the epitaxialmaterial has (111) crystal index sidewalls touching the first and secondSTI inner sidewalls.